Except for Henry’s Regina’s son too and it’s not Emma’s right to delve on. Forbidding her to see Henry was simply not something she could make decisions or ‘give chance’ on.
I honestly keep wondering when did that happen that it’s Emma who’s to make decisions whether Regina can see Henry or not. Nothing changes a fact that Regina has been a mother to Henry for 10 years, whether she’s an evil queen or not.
Even mothers in prison are often allowed to see their kids or even raised them there.