Clashing friends - please help!

Ok, there's this one girl I've been friends with for 6 years. We go to the same high school and everything. But just this year a girl transferred to my school with whom I've become really good friends with as well. I'm a junior, and during my sophomore and freshman years I always sat with my old friend at assemblies. But now I've been sitting with this new friend and hanging out/talking with her more in school than my old friend. My old friend is getting annoyed. I can understand that, after six years, she feels kind of abandoned because I'm not spending all my time with her. But this new girl is someone I want to spend time with as well. The biggest clash is in gym class, where all three of us are there together and I feel like I have to pick one to talk to and the other one gets offended.

I know you might say "talk with one about it" but if I do, they won't know what to say or will even consider breaking off the friendship so as not to conflict with the other. I can't bear that.

Oh, and did I mention these girls are polar opposites? The old one is studious, polite, very connected to her family, and follows the rules (that sounds like she's a dry person; she's actually not.) The new friend is rebellious, barely connected with her family, an extreme procrastinator, and much more open-minded. They must be the opposite sides of my personality or something. But the two of them, because they are SO extremely different, refuse to become friends. Not conciously, they just don't fit well together.

What do I do so that I'm not constantly feeling like I have to choose?

You never should ahve to chose between friends. Just make time for both. That's what i do! I mean I don't really hang out with ppl outside of  my grup but i mean when ur in the jocky group. well yeah but theres one girl who just moved here n me n her got really close she was awsome just like me till i found out she was into some abd things i still gave her the benefit of the doubt that she could change but really i wnet backi to my old firends. ALl i remember is that id spend on night with her n other nights with everybody else. Never choose just becareful!

I thinkkk, that even though your old friend has been your friend for so long, she should understand that you can have other friends and if there really gonna get mad about something so silly like you sitting with another girl at assemblies, then you guys probly just need a break. And when she feels lost without you she'll be happy with spending less time than before with you instead of feeling abandoned. People change, so just hang with who you want and don't worry about it,