Delicate subject (at least for me)

So hi ladies I need to vent and also I need advice. So I have an amazing husband we’ve been together for 6 years and married for 2. We have a 6 month old baby boy.. so the point is he had a daughter before we were together but the little girl’s mom kept telling him she wasn’t his and created doubt. Since we were together he told me about her from day one. Years passed and the little girl’s mom always kept messaging him asking for money among other things. He demanded a DNA test. She would say she didn’t want to put her daughter through that. Anyways now the little girl is 8 and wants to meet her dad so her mother stalked me on social media to get a hold of my husband. Long story short, my husband spoke with the little girl. I saw her picture she’s beautiful and looks just like him. But I just feel overwhelmed idk what to think and idk what her mother’s intentions are. I obviously want him to care for her because I am a mother and I love my son and don’t want to be selfish, but this is all too new for me. What should I do?

P.s. he’s going to do the legal stuff but there is no denying she is his daughter. I just don’t wan this to affect our Marie he. Has anyone been through this?