Friendship advice please..?

im 17 and in sixth form, it seems from the beginning i have made an effort in my skl to make new friends and i have. but the friend that i went to with before comin to this skl attends it as well. she has adjusted weirdly to the skl because she has neva been in a mixed skl before. she kinda acts desperately towards guys and it shows. im friends with her and vice versa but the other girl who i made really good friends with has made friend with her. im not jealous but my old friend has kinda swooped in and taken my new friend away from her. i try to organise trips with my new friend and her to go out but my new friend always seems to be buzi and in this half term she said shes makin plans with her old skl friends, which i understand but today on msn she said she went to london with my old skl friend. i was like 'really?' in a polite manner. but i feel depressed because it seems that this new friend doesnt like me as in the beginning. what shall i do? i feel neglected?