24M accused of incest by 23M

Currently in a LDR, my girlfriend is worrying that I might cheat and she asked me how do I meet my needs. I said I goon and she asked me what kind of corn I was watching?

She accused that the pornstar I was watching resembles my sister, while I do not find them lookalike at all besides being the samw ethnicity. I tried to explain to her that they don't look the same and she gets more upset for defending my sister. She even said that she is embarassed that I am into incest when that is a strong defamation.

She said I should validate her feelings even tho she is being diabolically wrong. Need advices before breaking up.

TL;DR: She accused I am into incest when I am clearly not. Advice needed.