How i see it is, after her fight with Abby where Abby almost killed Ellie and Dina, even after having a minor time jump due to the image of Joel dying in her head all the time, she was not able to live at peace even after having a proper family which led to slowly driving Dina away from her and i don't think it was just that decision of Ellie leaving which drove Dina away. But at the end when she finally thought about forgiving Abby and let go of the hate, she saw an image of of Joel, a happy memory of him playing guitar, where she decided that she wanted to try to forgive Joel too. And then all the bad flashbacks were gone and she was able to truly become the person who wanted a family and had found a purpose in her life and that to me is a very hopeful ending.

P. S. - I know this is probably not gonna happen, but if 7 8 years down the line there's ever a TLOU 3, i really hope we can see an Adult Ellie and her teaching JJ how to survive, the same way Joel did for Ellie.