Vegetarian do's and don't?

Most of those things sound fine. Unlikely, but possible hidden sources of meat might be:

-pork or pork fat in the baked beans (I know you said no meat in them, -but if they're from a can it's always safe to check the ingredients)

-lard or tallow in the dinner rolls

-rennet in any cheese products

-if the stuffing comes from a box or a bag it very likely has stock or meat in it, even if it's, like, "cornbread stuffing" or "herb stuffing"

Read the packages on pre-made stuff like baked beans and stuffing. No matter how you cook it, it might contain meat anyway. Baked beans usually have some meat, unless they're specifically labelled as vegetarian. Stuffing sometimes isn't veg-friendly, though it's usually okay.

Add-on: Don't listen to people who say that plain vegetarians (non-vegans) will eat marshmallows and the like. This is usually not true. I am not a vegan, but I certainly consider marshmallows to contain meat, and would not touch them.

Is your friend a vegan or a vegetarian? I don't eat meat but at Thanksgiving I'm happy eating all the side dishes. Vegans would not eat anything with dairy or eggs so marshmallows are the least of your worries.

You're right, marshmallows are a no-no for vegetarians since they contain gelatin. If your friend eats dairy and eggs, though, it sounds like you have plenty they can have. One thing you might consider, if you're planning a stuffing for the turkey, is making a separate casserole dish of it to bake in the oven instead of the bird itself. Make it with vegetable broth instead of turkey drippings, so your friend can have some. Otherwise, I think you've done very well. You're a good friend!

Everything there sounds vegetarian. You're right about the marshmallows- they aren't vegetarian but if you're making something with marshmallows you can use marshmallow fluff. It doesn't have any gelatin in it.

Gelatin is one thing to look out for - it's in Jello, marshmallows, many candies, etc.

Rennet is another - look at the cheese you use and make sure it doesn't have any.

You're very considerant for doing this.

I see a lot of starch. Maybe have out a fresh salad bar with fruits and whatnot. Vegetarian's can eat vegetables, fruits, nuts and oats.

Good luck.

I'd like to point out it's very kind of you to be thinking about her and her lifestyle choice when you have so many other things to plan for this Thanksgiving Dinner.

If she'll eat cheese than she isn't considered vegan and she would probably eat marshmallows. If she is not vegan and just vegetarian, then she should eat everything but meat and maybe eggs.