Really you can build almost anything in your house. If you move, though, you could be expected to take it out. (or if you get caught) I have never had un-invited code inspections personally, but I have heard of it happening when certain types of construction materials show up at a job site and are left out front.
You can have any number of fridges in your house, of any size - they won't stop you. An Indian-style kitchen would have a gas cooktop on a counter, probably 2 burners. (be sure to install an outside-vented fan and make sure it is used every time - this is not so common in Indian kitchens but a safety issue in USA houses.) No disposal needed to meet India standards.
Still, you have a problem. MIL is in your house, and bored. If you flip the deadbolt to keep her out of your half of the house, she will take offense. Your husband will slip her the key and she will let herself in anyway.
You need to keep her busy, find her some friends (a husband?) or get her a place somewhere else. If she is Indian, next to the temple would be good and she could socialize there. Maybe you could move to Minnesota where it would be too cold for her to follow you.
It is hard to know what you are signing up for with a non-US MIL. You need to work this out with your husband.