It's major spoiler, so try not to read any further if it's a problem.
And it's not answered in Tappan's Spoiler Notes.
Without further ado:
We know that Makoto is around enough to manifest, and even positively affect the goings-on in the real world. Tappan's interpretation is that she became a kami. I am not exactly sure what kami's status is, but we know that deities of the kind may have a significant presence. In Dog Days, for example, Yuki(kaze) is an active character. Then we have Kamichu, Wagaya no Onari-sama playing with the concept. Unlike Mr. Christ's mode then, it does not take a major miracle for a kami like Makoto to be an active part of human affairs, in anime anyhow.
With that in mind, are Yuuichi and Makoto still married?
See, if she were a Western character like Obi-wan Kenobi, it would not be a legal problem. Dead is dead and that's that. Here though, I'm not sure.
Anyhow, does it matter?
I suppose if she's kind-hearted enough, it does not. However, it could be a problem otherwise. Remember that anime about the ceiling ghost husband watching you have sex? If Makoto gets even a bit jealous, there's no telling what she may do. She's a kami after all. Dream haunting could be just a small time mischief.