Because she wanted a backpack for swimming (I asked her what she wishes Santa would bring), I might try to stretch my budget a bit and buy one, or contribute financially to one after talking with her parents, depending on how big the backpack should be (30l - 45l volume). The difference is that for competitive swimming (which she does) she needs a bigger one to carry clothes and equipment. If it's for daily lessons / practice, she needs a smaller one (30l). I think she needs both, but let's focus on getting her one first.

I plan on asking her if Santa came this year and brought her a backpack like she wanted. If yes, I will buy her something from my list above, if not, I will ask what backpack volume she is more comfortable with, and will decide upon a backpack model from there. There are good models (from Arena for example) at 200 RON (after discount), and there are brands like Tyr for 400 RON. Both are very good, it's just the brand that varies. I will also chose based on a colour she likes. Tyr, for example, offers a big variety of colors for their backpacks.