Just ask her, save a lot of worry man
The way you phrased what's going on makes it sound like her friends have passed judgement on you and deemed you unworthy and your friend cares what they think. It could be anything though. Maybe she is busy and seems that way. I have a feeling she doesn't feel the same way you do.
1 little word.... jealousy
3 little words she wants your attention back
i bet her friends noticed and pointed out to her that, hey- you like her. so now she knows (maybe she didn't, or only suspected, before), and she's..digesting the information. rotcod made a good point that could be a part of it, too.
Were you very drunk ?
propose her now, she's in love with you..
People sometimes act differently around different circles of people. I have known one friend who broke down in tears because she didn't no how to act or what to do when her different circles of friends finally met. Your friend might just not know if you think differently of her, or not how to process the "different worlds" colliding. I am not positive that is what is happening, but you can always just ask her. Let her know you had fun, and you still love her, and just want to know if everything is okay.