it seems to me that it would be nice to link the heroine’s Broadway goals (and feelings that success is increasingly impossible) with the niece’s wish. Something that would make both of them happy.
One possibility for the heroine and hero to get together is she’ll have to discover fulfillment in the small town. Could her mother push her into directing a hometown play or musical? (I know this theme screams Hallmark movies.)
The heroine has to have or know something that will bring joy to niece, but how can she do it without seeming conniving to the hero. Does she know the hero before she returns home to care for her mother? Do they have a past? Did she break his heart when she left to pursue her Broadway dreams?
Or does she need his advice on a matter related to her mother? How did she and the hero meet?