I mean, what sort of kiss? Are we talking a quick peck or a full on passionate kiss? If it was just a quick peck I'd think nothing of it, unless it was on the lips, then I'd have some questions.
What seems a bit odd that they she always seems unsure about getting married despite clearly showing some sort of interest. That's something that makes me double take. Speak to her about it. Maybe she's just worried about it because it's a big step in life, and weddings are usually pretty costly. If not that, she's either not interested in you, or she might be hiding something else.