since they were together for a couple years, mint probably came to see arlo as part of the family and thought it was really weird when they suddenly weren't together anymore, so maybe she kept up with him a bit and texted now and then, just because it felt awkward to cut that relationship off totally? especially if things didn't end on a bad note, she likely wouldn't have ill will toward him or anything and would still care for him as if he were part of her family.