Best bet is to try something I heard a friend do. As soon as she moves in, the same day, show up with the whole family and start pestering her about meals. Show up to drop off the grandchildren unannounced. Claim your washer and dryer are broken and show up to do your laundry for the last two weeks while complaining about the lack of good coffee and snacks. Don’t even give her a chance to show up at your place and make sure that you emphasize that you will be expecting her to really jump in there and provide child raising support and financial support when you run a little short. Think of every horror situation that you can imagine and then visit it upon her.
I have always found that the truth is the best weapon and the most unwelcome. It drives away the worst offenders.
I'm a MIL. The day my son married I told him and his new wife, "I will never come to your house unless I am invited." After 12 years I've not broken that promise. Five of those years they lived just down the block. I have kept both their girls full time. The older girl will be 10 this month. The baby is two and I'm still keeping her until she goes to pre-school. I feel fortunate that I have been able to keep them and bond with them. The girl my son married is a teacher who is all business. I don't feel that we have ever bonded, but I think she is exactly the person my son needs and I love her for that and because she gave me two beautiful grandchildren. I am blessed.