Tough love. There's no way around it. Give her two weeks to get out then put her stuff on the front pourch and change the locks on the door. You're being a worse parent by not teaching her to be an adult. What happens when you die? You are in your 70's and it's around the corner. It's time to be real and tough....she'll thank you someday! She'll find a place for her and her child to stay. It's never to late to be a good parent.