i just have a couple of comments. Ensure when you are correcting her that you don't use her name, rather use trigger words like leave it or off, etc. Make sure your male knows the correction is for the female mounting, not his growl which is appropriate in this situation.
Lastly, I would redirect in this situation, meaning redirect so she knows what is appropriate such as throwing a stuffy or praising her right away when she gets off him on her own. If you can intervene and redirect before she actually mounts, that may be helpful too so she learns what is appropriate behaviour.