Is it ok to list reviewing experience in a resume when you don't have a PhD?
If she has reviewed for these journals, then she has, regardless of who asked her to do it, and she can certainly put it on her CV (it's accurate and she can back it up).

One caveat would be if she wrote the reviews but they were submitted under her boss's name (with the journals' agreement) - in that case, it would be important for her to make clear that she was doing the reviews in lieu of her boss, and wasn't asked to do them in her own right. In other words, she certainly has the reviewing experience, but was asked because of her boss's expertise in the field and not her own (even if she may have that expertise as well).