I got jealousy vibes off of Miyu during her speech as well, though I think they were probably well under the surface for her. On the top layer I agree with Ryll that she has valid points about the problems Illya presents to team combat, however the obvious 'logical' solution to having an undisciplined powder keg of raw talent as a partner is not to throw them away but to help train them to control themselves and be more wary. Especially when it's been made clear in the last two fights that Miyu can't get the job done on her own while Illya can get it done with no sweat when she cuts loose, though she lacks control when operating at the necessary level to get cards. Unfortunately, Miyu doesn't seem to want to admit that she's totally outclassed by both Illya and the latest cards, so a Gilgamesh beat down is probably going to be necessary to give her a wakeup call.