Personally I have shared rooms with friends and friends of friends multiple times with no issues so I wouldn’t end up in this situation myself. But I can see both sides, you want to be comfortable and you’re entitled to that, and these things are expensive so she wants to save money.
I think you need to decide how much this friendship means to you. If she’s an important person to you then you need suck it up for your friend because this is a really big deal and a once in a lifetime special day/event for *her*, and you want to be there for her and make it as enjoyable as possible. I’m assuming you’re a close friend if you’re one of 5 people she’s invited. Chances are if this girl you’re sharing with is also a good friend of your friend you’ll probably get on pretty well with her. Even if you’ve never met her before.
It’s pretty clear if you pull out or get your own room you will be causing a lot of friction. If you do decide to do that you’re going to be damaging if not completely ending the friendship. So imo you either suck it up for the few days for your friend or you damage/lose your friendship.
