I mean she was 10 when we first see her but yes, right now, she would be around 11-12 or just a tiny bit older, but definitely not as old as Red (19-early 20s)
I think the important part that Terence is trying to convey is that Scarlet can at least have babies. There’s no point in finding another Wisa woman if she’s unable to have children in regards of reviving their clan