Okay, the break up occurred seemily because Megan started to mentally reduce people into vegatables, a bit like Identity Crisis made Batman overly paranoid of Zatanna and other meta humans.
If I had to guess, it happened to one of Queen Bee's people, or Queen Bee herself, when she killed Garth's mother. The Koolatarian attempted to kidnap her and Garfield.
Telepaths are a sadly misunderstood people in DC
Yet, their feelings remain....