In the novel, Marika says she will never date Aya because she's not that "type" of girl (a lesbian) and Aya replies that it doesn't matter because she can make any girl fall madly in love with her no matter what her "sexual type" is. Yep, that's right: het, bi, queer, gay, whatever they are, Aya gets all the girls, like pokemons!
Course maybe she didn't mean it: it could have been just a smooth line to impress Marika. From that angle it works great, it makes Marika breathless as she thinks WOW, Aya is such a CHAD!
Hehehe, actually the word Marika uses is "bari tachi" which is not exactly a chad. It comes from the Japanese classing of roles to take in bed:
バリタチ (bari-tachi): totally dominant, always on top and in charge
タチ (tachi): dominant, likes to be on top
リバ (riba): can go top or bottom, likes both
ウケ (uke): submissive, likes to be topped
バリウケ (bari-uke): always on the bottom, couldn't even top an Itou Hachi loli
There's more nuance but that's the gist of it. Marika calls Aya a bari tachi because she's so cool and confident, she's always dominating Marika, she boasts that she can make any girl in the world submit to her, and (this is prolly most relevant) when they make love she always pleasures Marika in an intense way and makes her cum again and again, but she never asks Marika to do the same thing to her and (as far as Marika can tell) she never orgasms and just gets her enjoyment from watching Marika's reactions before, during and after sex.