There isn't much time for a reaction. However it is he feels about her father, whatever suspicion and caution there is exists for Vader. Even on Bakura it had been the Skywalker in her, not the Vader, he'd tried to remind her of. Something more of Luke, of someone neither of them had known until now.

"Wouldn't be here if I had a problem with it, sweetheart." Han squeezes her hand and smirks, giddy and stupid and insufferable. "Though I gotta say I liked the sound of 'Leia Solo,' too."

Not a proposal, of course, but if they're being honest...