Tell me about it. I blame the writers really.

I think I may have to tell her it wasn't a date in the beginning because the last thing I tried was to tell her it's too soon and hurt her feelings (and mine). I didn't play anymore of that save because I didn't care to see her more upset than she already was. It does seem to be a make or break moment at a very early stage of the game compared to the other characters. Aside from Monica I guess you can put an end to thing permanently with her very early unlike with Katie or Lilly for example where you can see how things go without having to say right then and there that you are in fact together.