If she's someone you've talked with a fair numbers of times and found fascinating then we're in a reasonably common set of circumstances. I can certainly sympathize with a fondness for cheerful humorous sorts. The upside for you is that such people are typically the most approachable people around, arguably the ideal people for the socially awkward to chat with. So you presumably know her well enough that if circumstance puts you together you don't need an excuse to strike up a conversation, you just don't expect fate to provide too many of these and are worried you'll bungle it.

As to how to get to know her better and elevate it beyond occasional random chat, there is only one way, make sure your end of the chat is interesting to her. You can only influence two aspects of that, knowing what she finds interesting and being a good talker. Part of that latter is mode of delivery, the other is knowing how to fish for what someone finds interesting. Just about everybody likes to talk about themselves, especially if you've got the relaxed, open, interested manner going on and before very long you'll find a something mutually interesting to talk about.

With most people you can just smile, keep your eyes on their face, and simply repeat minor variations of "That's interesting" and always asking a question very parallel to the current subject but just enough apart to shift it to another subject to continue fishing until you find something mutually interesting. At that point you will naturally be less awkward and more relaxed because you'll be discussing something you both find interesting.