It's your own fault for actually watching the support conversation between Chrom and My unit, if you just left the support available without confirming it your could have gotten as many points as you pleased.
Although Chrom is the best first generation husband for My unit, so going that route isn't a terrible loss.
Accidentally? Well, guess you didn't know you going for pairings until just now, huh? Alas.
... Don't marry Donnel man, lol. That's not value (and it's Donnel... unless you're into the hick type, not judging!). Since Chrom and MU are already B, might as well ride it all the way. Path of least resistance!