I love Kenshin/Tomoe stories, and the idea of Tomoe's spirit faithfully following her husband is a beautiful one, hinted at in the OVA. The tone is sometimes a little too brusque for someone as genteel as Tomoe, but not precisely out of character--she was a woman of the samurai!
Kudos to you for not backing away from the very difficult challenge of reconciling Tomoe's feelings for Kenshin without denying Kaoru. One minor quibble: I have some difficulty believing that Tomoe, who set herself on a path of vengeance and, with equally strong will, turned away from it, would compare herself to Kaoru and deem herself the lesser. They are both equally strong, driven women, though it takes different forms.
(But I'll admit... I'm more of a Tomoe fan than a Kaoru fan, so I may be biased.) All in all, you did a great job with this story, with a challenging POV and interpretation of the main emotional story.