C.N.
It's perfectly normal for a 16-year-old to be attitudinous. They're at a difficult age - no longer a little kid, not quite an addult, and full of hormones they have no idea how to manage.
If all she's doing is giving you lip or being sulky, I wouldn't worry about it.
My daughter had a mouth on her, but I know she got it from me, and when I had enough, I just shot mine right back at her, reminding her that my attitude was bigger and I had had it longer.
She's now 20, and has grown into the kind of person I would want in my life, even if she wasn't related to me.