Fridging is real and it's a problem. But Rogue and the Scarlet Witch definitely weren't fridged. I think the best test for whether a woman's death is a fridging is to ask whether it is a culmination of her own arc as a character or whether she's being used in someone's else's. If you're going to argue that Rogue and Wanda were fridged, at minimum, you should be able to identify the character on whose behalf they were fridged.