I would say your vet is avoiding unnecessary antibiotic treatment for minor infections, as this then causes resistant bugs to proliferate
Many GPs are adopting this policy these days as well, BUT for me, any infection going on is bound to be pulling her down so at the very least, I'd want infection cleared up. Yes, it might correct itself with a first season, but what if it doesn't?? As I said, I had one with this and she was given antibiotics, the first course of which didn't work so we did a swab, culture and identification so the correct antibiotic could be given. No way would I have gone for 'wait and see'. She was a good quality bitch, destined for the ring and breeding - which she more than accomplished by coming with us back to the UK and taking a UK Championship. Her maternal career might have been equally outstanding had her one and only litter not met with a vet who didn't do a C.Section when needed = 9 puppies, 5 died. However, of the 4 survivors (note - not 'pick') 3 had their Stud Book numbers, one with a RBCC and the other with a BCC before being exported, behind my back, to Holland by the woman who I let have her and her brother (who also went to Holland).
Maybe had I'd just left her juv.vaginitis to 'resolve', none of this might have happened!!