GET A BACKBONE. You are Meghann's parents and all you can say is she won't do this she won't do that. Hello people it is your home and most importantly your grandchild. You need to make her take responsibility and if she doesn't you owe it to your grandchild to take proper action. If that means you have to take Meghann to court and take the baby because she is unfit, so be it. The baby cannot speak for itself and your daughter is 18 she can. If you do not, I promise you it will only get worse.
Ironically, your story is similar to my parents' story. This is how their nightmare started. When my older sister 16 and I was 14 (now I am 28 and my sister, 30) she got pregnant. My parents thought it was best that my sister have an abortion and so did my sister. So she did. After the fact I expressed my anger to them for what they had done. My sister claimed to be soooo upset over the ordeal and swore she would not let it happen again. My parents said they wanted to give her a second chance at a good life and if she had a baby at 16 she would not be able to do so. I don't care what others do, but when it came to my sister having an abortion, I was furious and hurt.
Seven months later my sister got pregnant with my neice. Once she was born my sister did nothing with her. My mom would come home from work and my neice would be in her playpen with food all over the place and bottles of curdled milk where my sister kept her in there all day. As my neice gets older my sister gets worse. She had my neice when she first turned 18 and now she is 30 and she still lives with my parents. Over the years my parents would keep my neice for weeks at a time (during the few occasions that my sister managed to move out for a month or two at a time). I would get angry at them because all my parents could say was well we try to make her take care of the baby and she won't so someone has to. I did not have a problem with them taking care of my neice, however; I had a big problem with them supporting my sister and her boyfriend even though they were not taking care of my neice my parents were. I moved home (from WV to OH) when I was four months pregnant. Granted it was myself and my son's dad. I was 17 and he was 19. We payed my parents rent, I cleaned up after everyone(including my sister family), and my son's dad did all the yard work in order to pay our own way. We moved out 10 months later when our son was 6 months old. My parents continued to do everything for my neice and my neice started looking a my mom like she was her mom. My parents continued saying well we cant make her do anything even though (like Meghann) it was their house.
When my neice turned four, my sister got pregnant again, and again my parents payed for yet another abortion. Their defense was that she did not take care of the one she had. After that less than one year later my sister got pregnant and had my nephew. Can you guess who raises him. That's right, my parents. Now my neice is 11 and my nephew is 6. My sister, who dropped out of high school at 18, still lives with my parents. She never has went back to finish high school, she does not work, she doesn't clean, and she doesn't cook for her children very often. My parents support her and her children 100% and now they are older and realize they are not going to live forever. So they wonder what my sister will do. They created that monster themselves by not giving and following through with consequences for her actions. Instead they chose to support her while enabling her (like you are enabling Meghann) to be worthless and do nothing to better herself. Chew on that awhile and think to yourselves is supporting her and not demanding her to do something to help herself really going to be beneficial. It's crystal clear, NO. My opinion on what you should so is set some standards and rules and if they are not followed then give her a notice to move out. If she moves out and doesn't take care of the baby despite all your efforts, then take her to court. Be the child's voice. In my opinion if my parents would of listened to some of the advice they were given maybe my sister would be a better mom, daughter, sister, and friend.
Last but not least I think that you both should watch what you say, your daughter does need support in order to succeed. Don't fail her now.