It's ridiculous that she says she hasn't given Jade anything. How about a roof over her head? No established, responsible adult targets someone like this when they smell blood in the water (break up) and within weeks moves state to move in with them, when they have their stuff together. She needed a place to stay. She absolutely got something out of this other than Amber's heart. They didn't even know each other, to be 'in love' and talk about wanting to marry one day, right off the bat. That's a desperate mutual grift, no different than how she and Becky coupled. It happened in almost the exact same way, with Becky supposedly reaching out because of concern, but the actual messages didn't seem anything like her being worried about Amber killing herself.
Funny that she got into the same type of fake relationship built on ulterior motive. If she actually put her on the lease, there goes any bargaining chip. She already isn't as controllable as Becky, now, Amber may end up having to be the one to leave, if things go left.
