I would call that "elementary algebra" or "pre-algebra", maybe. Google, Wikipedia etc. have definitions of algebra, elementary algebra, and pre-algebra so you can see the rough types of activities that would fall in each (and like ColinsMum posted below, the divisions are context-dependent and may not always make sense). The issue, and I suspect the sticking point for most people on calling this full-blown algebra, is that this is just a simple sum problem that kids can solve without algebra. I guess if your daughter uses a calculus method to solve it, though, you could fairly say she's using calculus!
It sounds like the teacher may have decided that you're simply a pushy parent, and that you're getting some push-back as a result. That's a tough one. If you want differentiation for your daughter, you may have to go over her teacher's head, get some testing done to support your case, consider switching schools, consider teaching your daughter the advanced materials she may need, etc. I am currently in the middle of trying to get some acceleration for my five-year-old son who's enrolled in public kindergarten, and it is slow going.
ETA: By the way, I made the same mistake a while back. I understand that it is exciting when you see your kid learning such things for the first time. I think ColinsMum's advice is entirely sensible, that it's better to talk about the types of things your child can do than to get hung up on labels.
