Sounds like a perfect time to take care of Sir Jury for Hermie. My Noodle went into heat at about 5.9 months - but fortunately she is around all fixed kitties.

As far as I know, even if she did have her first heat, there wouldn't be anything terrible about having her fixed after that. The only problem I know of about letting cats "mature' is that male cats sometimes start marking their territory and don't stop even when they get fixed.

Good luck to you and Hermie - tickle her tummy for me!