Hi, I hope I can shed some light on this:
As with any car at 90-100k miles, suspension-wise it's ball joints, tie rod ends, rear shock mounts, bushings, sway bar links, potentially wheel bearings. A rough life could mean subframe bushings (a rather large job).
Exhaust replacement/repair is probably imminent depending on environment (salty roads etc). Brakes should be checked; cooling system... did they replace antifreeze regularly and thermostat, water pump etc? If not, then you'll probably have to do it eventually.
Regular maintenance, and a full service history is a must when I'm looking at cars. Fewest previous owners is best. Go for low mileage if possible, but higher mileage and service history might not be so bad.
It's a tricky mileage to judge because many wear parts are at the end of their service lives and either need replacing or will within the time range your daughter is considering owning. It would be great to find one that has just had its suspension parts replaced. I just sold a 1991 318is and I had just replaced most of the suspension mounting bits.
Good luck, and I hope you find the right one!