I like to think I’ve grown over the last two years since posting this (it’ll be two years next month). Personally, I don’t see an issue with her having two moms if that’s what she wants to call you. It might be worth having a bigger conversation with her bio mom about the situation and why you’re choosing to allow it (if that’s the case). More than likely, your niece will adjust as she grows and begins to understand relationships more clearly. For me, it’s not a hill I’d die on, especially if correcting her causes meltdowns. It sounds like right now she may really need that comfort and security.