I would totally read a good Lizzie going quasi-Munchausen By Proxy on Tommy. Starts with something small, a cold that she overreacts to and treats like it's deadly; Tommy knowing but letting her because he's tired, taking the pills, taking the pills. Lizzie realising he's letting her but incrementally testing these boundaries with more and more removal of (self) control and independence. Until one day they realise it's all too late to exit this strange and horrible thing they've created.

Could totally go for this with Polly instead of Lizzie, too.