Yeah, Robin and Jasper definitely had some issues, but they were totally on her end. Combined with her normal hate-everyobr mentality, the added jealousy of her sister having a close relationship that isn't her would cause lots of friction. She would have grown to tolerate him for Riley's sake, plus knowing that he wasn't a bad guy. But yrah, there will be tension.
As for Rhett, she needs laid back people in her life, and pot certainly helps. If he can get past her initial prickliness I can see them getting along.