My best friend is in a long-distance relationship, and when her boyfriend visited her, my true feelings for her were evident and confronted. I knew she was in a long distance relationship since I met her, but I never met her boyfriend in person and didn't worry and when she thought it would be a good idea for me to meet her boyfriend it made me sick. I tried avoiding seeing her boyfriend but it backfired because it made me so much worse seeing her happy with him. Its not jealousy that's the problem, this girl is in a relationship with someone else and it pains me because I really really like her but don't know what to do about it. She's the only person I can see myself with and I have strong feelings but why try if I know it won't work with us? I'm getting mixed answers, "if you like her fight for her" and "leave her alone because she has a boyfriend"

She is in a relationship. She is not available. Be her friend with no expectations or leave her alone.

Think about it this way, if you were in a relationship would you want someone trying to take your girlfriend away? Any person who would allow themselves to be encouraged to cheat or leave their partner is someone who isn't loyal or trustworthy. If they will do it to someone else, they will do it to you.

You need to back away from her and give yourself a chance to meet women who are available.

Actually it IS jealousy. You are jealous of her with him. I think you mean you are not envious of him.
It is difficult to be best friends with someone of the opposite sex when you are both heterosexual. It's tough enough just being friends with anyone who prefers to spend time with someone else! I knew a gay teen guy who was upset when his best friend, a girl, got a boyfriend. Both girls and boys who are best friends with their own sex get jealous when one of them gets involved romantically with someone else. It is characteristic of being young, and most people learn to drop best friend jealousy as they get older.

Unfortunately, it returns when people are dating, lovers, and spouses... so force yourself to put a lid on it NOW. Or your entire life will be miserable.

BTW, hiding true feelings from someone strikes me as contrary to being best friends. Best friends hide nothing from each other.

Go with the leave her alone she has a boyfriend, since you don't know what to do about YOUR feelings, and seem to have no boundaries of good behavior to guide you.

No you don't fight for someone that DOESN'T have the same feelings that you do.

Appreciate all the advice and answers.

Also, she was mad because I accidentally told her I didn't want to meet her boyfriend (why would I?) when he visited and was trying to avoid them to "give her space". I ended up seeing her happy with him and it made me realize those feelings.

We are in our early 20's by the way. I'm NOT saying I want her to dump him for me. I had feelings before but was in serious denial. I understand If I had a girlfriend, I wouldn't spend a lot of time with my best friend all of the time and vice versa, so I believe our friendship will begin to fade as they my friend gets closer with her boyfriend and she'll forget about me I don't want that to happen. I've never expressed those feelings or flirted with her or shown those obvious feelings, and I kept distance at times and I made sure not to interfere with there relationship. I don't expect her long distance relationship to come crashing down and her to come running to me.

Our friends don't forget us, so that fear is unreasonable, but they can get busy with other things in their lives that they must deal with, and that's really okay. Friendship, doesn't have to be forced, it's a natural thing, nor does it have to take constant attention to maintain a friendship. You must maintain a proper balance within yourself of self control and restraint, good orderly direction, and proper behavior.

Sometimes in a shared friendship, meeting and respecting the people in their lives, is something that occurs between friends. You cannot be a good friend if you cannot accept that, without fear, jealousy, or envy.