I don't get this. All we know about Chapel in TOS is that she's a great nurse, had a fiance who got lost in space and turned into a robot, had a huge crush on Spock, and - when she did show any other personality - could be pretty cheeky. How does this contradict anything seen in SNW? Her reluctance to commit could either be a result of losing Korby or setting up an arc in which she falls for Korby (depending on where we are in relation to her relationship with Korby at this point). Her being more subdued in TOS could be a combination of her lost love, unrequited love, and just not being in her 20s any more...it all works fine for me.