Yes ladybugs are cannibals and will eat other lady bugs and even ladybugs will also sometimes eat other ladybug eggs.
I've seen one ladybug eat another ladybug in my backyard the other day when I was out there.
I've heard of ladybugs being cannibals and eating each other but that was the first time I saw in person a ladybug eating another ladybug.
I have seen frogs eating ladybugs and even lizards eating ladybugs but it was surprising to see in person a ladybug eating another ladybug.
The ladybug was still alive when it ate the other ladybug but it killed it and then ate it.
So yes ladybugs as well as some other bugs are Cannibals.