Aggression is not the issue. She is not aggressive at all. She just won't open the end of her abdomen to allow mating.
Had the same problem this past yr. One particular Chinese female simply refused to mate. On occassion she was aggressive toward the males. (Had that problem a couple of yrs ago and it took numerous tries by 6 different males before that female "allowed" one to mate her.)
But when this particular Chinese female allowed them to mount, nothing happened. The male stayed on her back and tried to mate but she wouldn't open up. It took about 2 weeks and 5 different males but finally she allowed one to mate with her.
Sounds like this may be normal in nature and if you're using garden variety mantids (Chinese, Carolina, etc...) call it quits and let her go back into the wild unless you are patient and want to continue trying.