[Christien]

Get an acoustic cello. They're no louder than a tv, and I really can't see it bothering your neighbors, even if you live in a 100-year-old apartment building. Electric cellos are usually just acoustics with a pickup (mine is). If it's a solid body, it's probably very expensive, and not a good idea for a beginner.

Go to a proper music store that sells used gear to students. Get a student-level one, should be under $500. Get a full-size - 1/2 and 3/4 size are for kids. Any decent store will allow you to exchange it if she's not happy.

Awesome idea for a present - I'll bet she loves it!