Interesting case.
Your friend lacks some social sense. You have strong social sense. You are afraid of saying no to a friend and this unreasonable friend is causing you pain. Put it simple. You have to tell her something directly such as “Normally I welcome friends to come to my house and join us for dinner. But if they come very often, it’s better everybody take a dish with them so I don’t have to cook that much.” But now you are going to have a baby soon, so you don’t even need to say those, instead you can just say “ I will give birth soon, and now is a special period for our family. We have tons of things to prepare for our baby; I don’t want to have a party. When I have time and energy I will have a party for our friends. And you can come.”