calling in the whaling experts

I was whaling on Peggy cover I managed to get 2 cover by resting the vault so after that I reset the vault a few times but no Peggy so I was wondering if there is a limit on the same 4* character I don’t want to be spending to much money as you know it doesn’t grow in trees any information would be great

Two random fourstar covers in a vault.
41 different fourstar characters to fill those two spots.
There’s one chance in twenty Peggy shows up.
You’re probably better off saving your HP for a later vault.