I think if Ronnie had stayed around, there was a better chance of her changing - for both Paige and Ralph. For one thing, I think Paige would impose a pretty tight rein on her contact with Ralph if she felt being around Ronnie was in any way harmful to him. Ronnie may be more motivated to straighten up in order to continue her relationship with Ralph than she was for young Paige. As much as I'm sure she loves Paige, Paige was a responsibility, while Ralph is more fun. The responsibility part may have actually dis-incentified Ronnie from changing for Paige's sake.
Having seen that Paige really does care for her mom - even if she would rather she didn't - I hope she occasionally asks Ralph how Grandma is doing.
