Is it good to have friendship with a guy who is in love with you while you are in a relationship with someone else?

Sally is using Harry to prop up her ego, and as a fall back position.  As she plays Joe off Harry, she knows she will have one or the other, and for now, she has both.   And Harry is actually a Dick.  If he had half a brain in his head, he would realize he is being strung along, and find Mary - a woman who really likes him, and would be thrilled to be with him.   Harry has free will, and can leave at any time.  He doesn't have to rely on the actions of other people to determine his actions.   And there is no reason for Sally to change, right now, she has it all.

It sounds to me like you've already made your choice. You could have named the 2-year boyfriend Harry and he would have been the Harry to your Sally, just like the movie. But, no. You gave the long-distance boyfriend the nickname of Joe; the average, boring, standard nickname that no one ever chooses to name the one they love. Far fetched? Maybe. But when given the suggestion to change your XYZ characters to Harry, Sally & Joe, you gave the "friend" the nickname that naturally pairs with Sally, and you have the boyfriend the generic, non-emotional nickname. If I'm wrong, that's fine. But I'd also like to make the point that if you spend enough time with a person (Harry) you might end up falling in love with him too. You should either cut things off with Joe and embrace your new 300-mile-away-from-the-ex-boyfriend life with open arms OR you should definitely stop leading Harry on by letting him buy you dinner and being your chauffeur. A man who buys you dinner and picks you up from work and tells you he is in love with you is often called a "boyfriend" so it's no wonder Harry won't give up. If you won't let Harry be your boyfriend, break things off so he can go be someone else's boyfriend instead. If that thought makes you sick, break things off with Joe and give Harry a big fat kiss on the lips the next time he picks you up from work. You have to choose, before one of them (or you) gets hurt.

I realize that this question is almost a year old now, but will add my answer anyways in case someone in a similar situation comes by. No, this situation is not alright. There are two mindsets which are particularly conducive to cheating. The first type (rather obviously) includes people who feel no guilt over the thought of having an affair. The second type are the people who think, "But I would never have an affair! Never!" One of the most important steps you can take to protect your relationship is to recognize that you are human and you are vulnerable to temptation. If put under sufficiently trying circumstances, there is a chance you would cheat. (for context, this is coming from a girl who has been ridiculously in love with her boyfriend for the past year and a half, and who can't even imagine wanting to be with someone other than him.) If you place your emphasis on "but I won't be tempted", that could be a recipe for disaster. After all, temptation is outside of your control. What if you are tempted? You will be woefully unprepared. A better perspective is to recognize what situations might possibly be tempting and, out of respect for your partner, refrain from those situations. Don't flirt with danger. A more comprehensive list of exactly what situations qualify as "potentially tempting" is outside the realm of this question. But I can say with absolute certainty that your situation might as well have a blaring siren attached to it. Why? To begin with, long-distance relationships are always somewhat more fragile than non-long-distance relationships. If Sally's time with Joe is largely restricted to Skype/Facebook/etc., but she is constantly making more tangible memories with Harry, it is not a huge stretch to think that she might grow to view her relationship with Harry as more "real." Surely there will be moments when Sally misses physical intimacy-- and in those moments she will have Harry by her side who she knows is readily available. Surely there will be times when she and Joe fight-- and in those moments, she will turn to Harry who will only be too eager to tell her that she deserves better. Note that things could be different if: i.) Harry was an extremely respectful gentleman who kept his feelings to himself after finding out that Sally was taken. ii.) Sally and Harry weren't becoming progressively closer over time. It would be one thing if Sally and Harry were lifelong friends and, after finding out about Harry's feelings, Sally scaled the relationship back but remained on good terms with him. It is quite another thing that she becomes very good friends with him despite knowing early on that Harry has strong ulterior motives. This must also be confusing for Harry. He probably won't be able to get over Sally if she is constantly with him... any increase she makes in the friendship will be perceived as a sign that she might finally be falling for him. It also must be hard on Joe, for rather obvious reasons. So, to the question asker (who I suspect is the "Joe" in this story)-- it is fair for you to be worried about this situation. Yes, it is fair for you to expect Sally to restrict her contact with Harry. But please bear in mind that Sally isn't doing anything abnormally terrible. Although her caring for Harry is actually making it harder for him to move on and is also causing you worry, she probably genuinely believes that she is just "being nice." As a final disclaimer-- I have guessed from your question details that Sally and Harry are becoming very close friends and that perhaps Sally is slightly taking advantage of Harry (with the dinner buying and picking up from the office.) It's reasonable for you to expect this to stop. It is not, however, reasonable for you to expect Sally to run away screaming from Harry everytime she sees him. They do work together and if she manages to tone the relationship down to a friendly acquaintanceship, you will have to learn to accept that.

Yes Sally can have a healthy friendship with Harry. Provided Sally is clear about the relationship, and explains her stance clearly to Harry. Else it may end up with lot of misunderstanding. It is important she tells Harry that she is in a relationship with Joe and thinks of Harry only as a friend.