My girlfriend acts differently around her family, can anyone else relate? - eviltoast

I go with my gf to her grandmas lake house every year, and while its relaxing and fun, I absolutely notice a change in her demeanor, I find I have to walk on eggshells around her and every other thing I say or do seems to be wrong and warrants nagging. I have confronted her about this but she seems to deny any change in behaviour is happening and just retorts with “well I told you xxx!”

Obviously her family is stressing her out but it kills me that she won’t acknowledge that, especially since I’m such a straightforward person who likes to discuss what’s going on. And that shes such a family girl on top of that. I’m planning on marrying her but i m just not sure how to discuss this particular point of contention with her first, because it’s one of the few things she’ll get actually defensive about