At her age, she is hormonal. Those hormones can cause aggression. If the vet said to wait until she's 1 year old, then he doesn't know what he's talking about. It is common to spay females at 5-6 months of age. She is well past that and should be able to be spayed right now. By delaying, it only allows the opportunity for those aggressive hormonal behaviors to become ingrained (habit).
When a rabbit is hormonal, they can't fully control their behavior. Sudden aggression isn't unusual so don't take it personally.
That said, rabbits do use body language to communicate. It would be a good idea to learn as much of you can about that. Here's a link (in addition to what I'll post separately):
http://language.rabbitspeak.com/
If a rabbit uses her body stance to let you know something, and you don't understand, then she could very well get frustrated. If she growls, then be on the alert and stop whatever you are doing. She is warning you. A lunge typically follows if her growls are ignored. That could be followed by a bite.
Hormones can come on gradually or all of a sudden.
{I'd look for another vet.}