I'm not so sure it's that bad, if they're made by reputable pet companies and she follows the directions carefully. Probably better than not worming them at all,and for 10 cats vets fees would be expensive. My guess is half the time for regular home-dosage type stuff it's all pretty much the same chemical drug, just vets charge more because they can! Like us having "homebrand" aspirin instead of a pharmaceutical branded aspirin.

If you really want your cat back, why not just tell her! You miss your cat so much you've changed your mind, she has 10, you don't have any (or only however many). You love her and miss her and want her back. I don't know the circumstances but it seems pretty simple to me

Good luck, let us know how you go