K.B.
Hi Maria-
There's no doubt you are in a very difficult position, one that I would NEVER want to be in so my thoughts are with you. Here's my opinion for what it's worth. If she is going to be staying with you for a while you all have to learn to live together happily. It will be miserable for everyone in the end if you can't all get together on things. First you need to accept that she is older and it will be difficult to change her ways. She has raised children so she thinks she is an expert and knows what is best. She has always been the lead female in the household so taking a backseat to you is not going to happen. You need to both learn to work together so that your family can run smoothly. For your part try to relinquish some control of the household. If you don't like the way she moved the furniture or the pictures just tell her that you prefer it the other way and move it back, but don't just get mad at the IDEA of her moving the furniture. Sometimes we just get ticked off at the principle of the thing and don't take the time to really look at what was done and see how we feel about it.
As far as your daughter goes, anytime you have someone else watching your child (whether it's a family member, daycare, a babysitter, etc) they are going to do somethings differently than you. You have to determine what things are important and what you can let go. As far as the food goes, things have changed since she had little ones and if your daughter is not ready for certain foods just tell your MIL and explain why.
My guess is that her moving in with you has been as stressful and unnerving for her as it has been for you. She is just trying to find her place in the new family structure. Sit down and talk to her to help her feel more comfortable with sharing your home. This could be a wonderful situation for your whole family if the two of you are able to sit down as mothers and work together to manage your family.
Most importantly, try to focus on the positives that she brings to your family. Your daughter is safe at home with a loving grandma while you're at work. You are able to work without having to pay daycare costs. You have an experienced mother in the home to ask advice of when you need it (although sometimes you might get it when you don't want it!).
Best of Luck,
K.