My dad is probably one of the nicest people you could meet, but is not talkative at all. I'm personally very observant when I meet people, so I don't talk a lot either until I get a feel for what type of person they are. Give it time and if he turns out to be rude, don't hold that against the girlfriend. I'm sure she can't control his actions.

It would be helpful to know how often you visit your MIL and how often your MIL visits you. If it's, like, once every other month, your MIL's cooking isn't going to kill you as long as she isn't using unsafe cooking methods that are going to give you food poisoning. But you could offer to help plan the menu, make a salad, make a couple of healthy side dishes, whatever it takes to risk creating a rift in your relationship with your husband and MIL.

Where is the 'suck it up' option? She's cleaning your house and babysitting your kids for free. Let her 'snoop', what are you trying to hide anyway?