Yes they are.

Dare! This is getting really fun, actually.

"Okay. How about this, then. I dare you to... take off your shirt." She grins.

No bra is easy, but sitting completely topless with Alison might be too much. She's already shown how devious she can be, and you'd be completely exposed. And, what if someone actually did come in somehow? It isn't like you completely distrust her, but it could happen. She didn't lock the door.