Are you offended by such posts? If not then proceed and expect more of the same.
If you are, then be honest and discuss your concerns. Why would you hide yourself from an old flame? Why would you suborn behavior you would probably not endure had you not already been "involved" with them? Either you have a relationship with openness and honesty or you do not. I am not sure why you even mentioned sex. btw, Dinosaurs are not involved in my reasoning.

You are best informed to determine the correct course of action.

If it were me, I would be most apprehensive about devoting much (captive) time with any theist.

I would quickly back out and politely but clearly explain exactly why I no longer wished to devote a chunk of my life to share with her. Sadly, I had a somewhat similar experience to this with an x friend (woman from work who retired) who wished to be my friend on Facebook. I warned her this would not be good for her as I have a low tolerance for superposition. She wound up being highly distraught when I mercilessly attacked her ridiculous theist based post so she unfriendly me.

I often confront (as a bit of a past-time activity) theists and for those few who don't run away, eventually, and politely grind most of them into the ground. On many occasions, I have driven theists to a point where they cry, assume the fetal position or, in the saddest case, crouch down and whimper like a dog that has been beaten whenever he see me.

You may be able to tolerate superstitious people and maintain a civil discourse with her - - In the ruse of a vacation, I'm not sure I would enjoy time trying to walk on egg shells to patronize her and and not obliterate a theists assertions.

I used to get a lot of posts on fb asking "Do you think we need more God in school?" like for no, share for yes. This simply causes those who agree to have a voice and does not give those who don't a voice. I would place a comment like Yes we do need more Zeus, Baal, Vishnu...etc. and then share. My fb friends stopped sending me those posts, and those who refused to respect my beliefs blocked me. Try this and if she really respects you, you can then make an informed decision and not make a decision without all the data. I won't give relationship advise without all the data.

Why get involved with an old flame that has gone wacko? I would avoid her whenever possible and you're seriously thinking about being trapped in a car with her??

My opinion is...Talk to the lady, her response will give you the answers you seek.

Sex is out of the question and you are going on holiday with her? Oh, so been there and done this and got the t-shirt. Just find a nice woman when you get there. Religion is not the problem here.

Where is it you going?

The earlier you back out , the better . Let her know before she makes plans , arranges for leave time from her job , shops for appropriate clothing/gear , etc. Don't put off letting her know , until the last minute .

That seams to be yet more of the verses of their holy book that they ignore.

Love is more than your intellect