Yeah way too much Benedryl. It is 1mg per pound. Unless your cat is 25lbs. If it was a 20-25 lbs cat you might be able to get away with it.
Excessive Benedryl will obviously make the cat drowsy so that could be why she is hiding. Other symptoms include vomitting, diarrhea, dry mouth and worse. Keep a close eye, or call pet poison control or your vet asap.
Yes, twenty five MG is way too much, call and talk to your vet and see what can be done. I have used benadryl for long car trips to sedate them, and they were sedated on much less, call your vet ASAP.Please call your vet and ask for correct dosages or research on the internet, i'll pray for him, please keep us informed!