You and Donnie loved each other a lot, even though you were a human and he was a mutant..

When fighting the Shredder's dumb minions, you were thrown into a large pool of mutagen.. Your body mutating..

When Donnie tried to help you, he saw that you tensed up and growled/hissed.. It was like.. "Y-You don't remember me..?" he whispered under his breath.