question about dog ACL surgery

I was wondering if anyone can give me some advice.

My small 7 year old terrier had ACL surgery last december. She's about
15 lbs. Anyway she had the usual recovery time and while she had a
couple of setbacks, she has seemed *fully* recovered for at least the
past 7 weeks or so.

Today on one of our walks she started limping on the bad leg again, as
if she'd had another setback. she seems very reluctant, but not
completely unable, to put weight on it.

Our vet had told us recovery would be long and she'd have setbacks,
but i'm wondering if this is more than that and if she's blown the ACL
out again. The original surgery replaced her tissue with Gortex so the
vet had said it was pretty unlikely she'd reinjure the same leg, but
not impossible.

has anyone else had a dog have a setback like this after seeming fully
recovered for a couple months? any advice?

thanks.

MG