Tofu is OK. I haven't been brave enough to cook with it, other than to cut some up into soup, but when I've eaten it at restaurants I like the texture and the flavor, which it picked up from the sauces of the food.
Tofurkey might be OK. I'd have to try it. Perhaps the MIL feels that she has been taken for granted and this is her way of protest. Before the day of the meal, the dishes for the meal should have been worked out with each person who was bringing something, especially with the person bringing the main dish. For a side dish it wouldn't be so important to check ahead of time, but there are usually several side dishes.