Given she may have read some more grown up novels for comfort in her later years she likely had and advantage regarding the direction things were going. As soon as she was brave enough to even consider the possibility of things playing out like that. Because Alphen was completely acting on instinct for his actions and his own heart for the words.

So when she tested his lips with her tongue, it was instinct that made him part them almost inviting her in to deepen the kiss to rock both their worlds.