When we were first married, the people from whom we were renting wanted their house back. They'd have let us have it for 6 months to a year, but they were DH's best friend's family and they were having their first child. He convinced me to let them have their house back. We moved in with his mother and took his best friend's lake cottage for the weekends. I lived there for a month before I couldn't stand it any more. I moved back to my parents' house and he lived with his mother during the week. We'd live together on the weekends. When it got too cold to stay at the lake, he'd stay with me, on the pullout couch in my parents' living room. We lived like that for 4 months.
My sister and BIL moved in with my parents last September while they were building their house. They had sold their house and needed temporary lodging. Luckily, my BIL likes my parents more than his own, so it worked out wonderfully for them. Additionally, they had the basement to themselves, as there weren't as many people living there as when I had moved back in.
It worked out for both of us. But, then again, we had specific timeframes for our housing needs. It sounds like your DD's needs are open-ended.
My parents always welcomed us back, even though it wasn't something for which they had planned. If you get along with your DD and won't get on one another's nerves, it can be a good experience for both of you.