Well, let's say concerned enough for follow-up. It depends on how much protein was detected. If it was trace, that often occurs, and is not a big deal, just bears repeating urines once in a while. If it was more than trace, I would ask to have other kidney function tests done including a urine protein/creatinine ratio and serum protein level.
What did her Dr advise for follow-up? The most thorough assessment would come from a kidney specialist, and I would do that just to be on the safe side and if there is a problem, catch it early. If she has any other problems such as fatigue, anemia, joint pains, rashes, or just in general not feeling well, a rheumatologist might be helpful as well. It is important to follow up on this, but not panic, as she will sense that and get anxious too, perhaps needlessly. Please let us know what transpires, and if you can get the level of protein, usually expressed as 1+,2+,3+, 4+ on a dipstick, that would be helpful.