Since their breakup, she’s had to watch him become increasingly erratic and irrational as it looks like he’s beginning to suffer from the same condition as his father.
And, Meredith actually cancelled her date with Cormac to take care of a struggling DeLuca.
But, even though Meredith and Cormac have tons in common and were able to bond over losing their spouses and having to raise their kids alone (not to mention that they’re both clearly into each other and he asked her out in the finale), Meredith is still very much tied to DeLuca.