Haha that would be funny. I don't think they would be able to hide for very long with her just popping in all the time. Unless it is when Clary is gone that they start dating. Logan would curse under his breath giving a quick look to Billie before looking at Clary. "You can't tell anyone about this Clary. Only Alex knows at the moment." 

Oh my gosh I bet that secret would damn near kill her to keep.

They remind me a bit of me and my sister xD

And Logan would just be smiling ear to ear at her. "No, you are glowing again. I've always kind of enjoyed when I make you do that."

Haha that just makes it funnier!!