Ah, I was in the exact same situation just a bit over a week ago, OP!
Mind you I was "your friend" in that situation. I travel a lot but can only afford to do it so often because I travel cheaply so cheap hostels are my go to place. I mostly travel on my own though, so don't really impose my personal likings on anyone ( plus I really can't be bothered with all the dramas that come with traveling with other people ) and I tend to avoid traveling with other people, especially friends, at all cost. A lot of my friends have a much higher budget than me and also seem to adopt that " let's just spend all our cash and not think about it " while on holidays as it's supposed to be the "best holiday ever" which means I am expected to spend hundreds of euros on a few days away with them when that would be my budget for 3 months of travels if I were on my own to somewhere more exotic than Europe!
One of my friends from Australia came to visit about two weeks ago and then insisted we were to travel a bit together around Europe, except she is loaded ( she works in an Hospital and make a minimum of 40$ an hour!) and I am not, her idea of the perfect euro trip was to stay in luxurious places and go out to 50€+ events most nights when mine was mingling up with other backpackers in local hostels and enjoying a pub crawl or local bars/clubs. I ended up having to compromise because she would not stay at hotels so we ended up in Airbnb's and I did resent her a bit for having been made to pay for much more than what I was willing to in the first place (not too badly as it is nice not having to share!
).
But from experience, accomodation is usually just the tip of the iceberg. Most of my friends who prefer more luxurious holidays also prefer more expensive activities/events/restaurants/ways of transportation.
If you don't agree on accomodation it is likely you won't agree on those topics either. Everytime I have made the mistake of traveling with friends I have ended up having to cash out for (expensive) things I didn't want to do because my friends really wanted to do it and really wanted me to do it with them (there is only that many times you can say "no I don't really have the budget for that" without being seen as the annoying friend that's ruining it for everyone!).
I don't begrudge people earning more than me and wanting to spend their money on accomodations they fancy or activities the really want to do but I do resent a little the people who expect me to fork out cash I don't necessarily have (or want to spend) on things I don't really want to do because they want to do it and need me to do it too to have a good time!
I think you need to speak with your friend again, talk about your expectations and so on so you can have a clear idea of what her ideal trip is.
To be fair, it doesn't sound great tbh and I would probably advice you to come up with an excuse not to go or only go for a weekend or so. Your friendship really may not survive this trip if you have a very different idea of the ideal trip and end up spending too much time with each other (especially as she is already calling you a snob!). I have traveled with a few friends of mine and I can definitely say our trips have modified our friendship. I don't dislike them but God I would never travel with them again! (and I am pretty sure they would say the same about me (
).