How to solve the problem of other cats battering open cat flap and stealing my cats food?

HiWeve got a Staywell magnetic cat flap with a magnetic collar for our cat. The problem weve got is that other cats are battering open her cat flap (even when we lock it) and stealing her food! We scare them off when we catch them doing it, but they come back when were out. Does any know where I can get a food bowl which only opens to a specific magnet? Or a way of discouraging these violent kitties? Thank you