One day I'd like to learn upright. My instructor is a Jazz Upright player, but carries his Fodera 6 when he travels. Depending on who he plays with (I think), he may bring his Ubass.
My personal guitar is a custom neck-through P/J (see avatar). For upright sound, not only do you want to stick with a p, but you may also want to get a fretless (ditto for a fretless Ubass). My friend has a custom MIA Fender, with a P at the neck, and soapbar at the bridge. It because of his sound that I made mine P/J. The J pickup by itself is to growly, but strangely adds a nice fat sound when blended with the P.
I've heard and played a Ubass (couple of them). its a cool bass, and does what it needs to do. I wouldn't get one personally. I don't like how it plays. It really is TOO small. I'd rather design a short scale (note: the Hofner sounds cool as well). You can do way more with flatwounds on an electric, IMHO. BUT, if size is the utmost importance, the UBass is almost impossible to beat.
Key point mentioned: daughter wants to get into more modern music. In that case, I'm biased, but I love my P/J, with flats. String changes to rounds give a completely different sound if needed.
Also mentioned: amps (and cabs). If she wants an "upright" sound, she needs to do research and stay away from baked in tones like Gallien-Krueger, as an example. My personal rig: Eden WTX500 through a custom fEARful 12/6 (which is sometimes known as a Super 12 in bass circles). I'm currently searching for a tube preamp to match with my Crown XLS 1500 amp. The Eden has a nice warm tone, but I ran a G-K 1001RB through the fEARful, and the headroom gave me a huge fat sound. The cab can take it, so I'm wanting to up the power now.