You will need to do alot of counter conditioning exercises with her.
Verbal corrections do not work unless the dog has a clear understanding of what NO is. As far as she's concerned your making some noise at her to momentarily interrupt her.
You need to write down EVERY episode of her exhibiting aggression (growling, snappin, lunging) and what was going on just before. There's a link, believe me. Something has triggered her and you need to find it, it's now become out of control and she's developing new fears, and possibly being rewarded by them indirectly.
It could have been when you got her spayed it was an extremely traumatic event for her and she now fears men? I'm not sure, not enough info is given.
And she has taken that fear from just the vet to outside, the fears will keep increasing if you don't do anything about it.
I would get a behaviourist, not a trainer (most trainers don't use positive reinforcement as they should, they incorporate domination and reward, which is NOT positive training). You could go for 1 or 2 sessions and learn more about your dog coming out.
If you can find a trainer with references give it a try.