OK so me and my friend sarah have been best friends for over a year. We do everything together. We never really had boyfrieds.. we were always the single girls in our group. Well we started bickering about a month or 2 ago because I wanted to get back with my ex boyfriend and she got mad.. so I didn't. But I recently got a new boyfriend and I told her when we started talking that I would always put her before him. And all of a sudden her attitude changed to me. She wanted to argue with me all the time over stupid things (like what I was doing) well this week I planned a surprise birthday party for her and it worked out great.. I thought. Except apparently not enough people showed up. And it kind of hurt my feelings cause I helped pay for it and I had to plan it all by myself. But I got over it and then she started attacking me through text. She would text me while I was hanging out with my boyfriend saying something like "use protection" and stuff like that. Than all of a sudden she's telling me all my friends think I'm a slut and she is sick of sticking up for me (wich I'm most deffinently not a slut) I don't think I have doen aything to her! And so I tried talking to her about it and all I got was "all you ever do is think about yourleslf and you dont care about me. you never give me good advice and you dont like half the boys i date" and she gets all mean about it. I'm trying to work it out. I told her she could talk to me when she feels like treating me like a human and not attacking me... she replied with " thats not gonna be to soon" I don't know what I did worng? Is it cause I have a boyfriend? I need advice!

She feels threatened by your boyfriend, is all. As people progress in their relationships, some people don't spend much time with their friends anymore, and the friends feel neglected.

Or, it could be she wishes she had a boyfriend, too.

I would talk to her about it and let her know (yes, I know you already told her) that you really mean what you say about not neglecting ya'lls friendship.

Maybe plan a sleepover or something and just spend the night talking and enjoying each other's company.

Teenage girls are moody and sometimes those moods and attitudes get directed anywhere at anyone.
She is probably very jealous of you being in a relationship and no matter what vow you take to put her first, she is still neglected and doesn't get as much of your free time.
That is what happens, it's how it works.
You may just need to give her the space she is after.

She refuses to talk about it... I tried last night. I told her if I had to I would break up with him cause our friendship was more improtant than boys and I thought everything was good but then this morning when I asked how her morning date went... she started mocking me.

Might want to look for a new best friend, then.

That's pretty ridiculous.

Sounds to me like typical high school drama.

My advice, get a new, less dramatic friend.

Don't waste your breath arguing with her. You have done enough and said enough.
I wouldn't give uo the boyfriend because then she knows that she can control you and you never will be able to have a boyfriend as long as she is around. You need to start sticking up for yourself without having to apologize for yourself.
She is jealous and nothing you say or do is going to change her from the way she is.

You can dump your boyfriend for her but then what you going to do when another guy comes along and she gets mad about him?

I think your friend is insecure and does not have lots of friend and she feel your boy friend will take your all attention. If she is your good friend just say to her that you are her friend but you have a life too.

Like Justwantfair said and I am quoting him

Teenage girls are moody and sometimes those moods and attitudes get directed anywhere at anyone.