I think it is more Lilly recognize Marika is still running around with Heteronormativity = on, though it's been severely weakened, and Marika is not used with very self-conscious about loving girls because it is considered normal in this world.
So she tries to be considerate of Lilly.
I mean, it's not that much different with falling in love with your straight friend, I guess? Except you also fake-date her. And it's your own goshdarn fault, because you compel her to do so.
Goshdarnnit, why would you do that?!