telling me what I can and can't do?!

And this one girl befriended me quickly but after the first few months I settled in and knew what everyone's like, but this girl keeps telling me what I can and can't say and how to act in school. She keeps saying she's been here longerso  I should listen to her about everything. She shushed me when I'm talking sometimes and is constantly making me feel a bit panicky and trapped with the constant shushing and the 'don't do that' She's a nice girl don't get me wrong, but were very different.  I feel a lot more comfortable around this other group in school  Who are in my chemistry class but here's the thing, I'm really close with this other person  she's friends with so I can't ditch her. the whole issue is making me feel trapped, but I don't feel like I can talk to her about it without shouting or offending her. Help please!