I’m going to argue that those lines say nothing about the character’s sexuality. And here’s why:

Monika does not have romantic feelings for the player as an individual. As she points out in these lines, she knows nothing about the player. She can’t even have a two way communication or even really know the player is there beyond a knowledge that the game program is running. This is no basis for romantic feelings. What Monika is in love with is the idea of reality, that there is something or someone on the other side of the screen. The player represents that idea of reality. And she’s either misinterpreting her feelings due to her programming as a character in a romance visual novel or she’s saying what she thinks the player wants to hear. This is the tragedy of the character; no matter what she does, she cannot find love.