Friend problems!! help!!!!?

im 14 and i have this friend and iv known her for ages and wev been best friends, well shes 1 of them, and i usually go out wiv her every sat, and i brought 1 of my other friends along too and shes been comin out with us a couple of weeks! and my friend is realli annoyin, she doesnt have many friends and im always ther for her, i give her clothes, help her out, im always ther for her and we never fall out, i think she takes me for granted, and i didnt let her borrow sumthin of mine and she was realli annoyed! i spend most of my weekends with her a this week i cant go cus im goin out with other friends! and she went and invited my other friend she hardly even knows to go out with her instead cus im away, and ther 2 of my best friends and i dont want them endin up best friends i regret bringin my other friend along in the first place! i dont think she apreciates me i always seem to do things to please her! and not a thanks in the world! then she got a new boyriend a while ago and she didnt talk to me for ages cus she was way too busy with him and then when they broke up she came crawlin back to me, i think she just takes me for granted, i just cant stand her anymore, i dont want to spend any more of my weekends with her, im just gonna spend it with my other friends, but i dont want her and my other friend bein best mates! i cant help but worry bout it! what shud i do! its hard bein 14!