based on the conversation with beaty, what might have happened to clarisse?

Montag mentions to Beatty that the “girl next door" was killed. Beatty sees this as normal and that Clarisse's family was odd.

“…She was a time bomb. The family had been feeding her subconscious .... She didn't want to know how a thing was done, but why. … You ask Why to a lot of things and you wind up very unhappy indeed, if you keep at it. The poor girl's better off dead." (Part 1)

Beatty does not consider a bunch of kids running over a girl like Clarisse to be tragic at all.