Girlfriend's s?

When eating dinner with my girlfriend, I'm always able to bring her right to the point of , but never to it fully. Sometimes this will happen as many as 3 or 4 times in one cunilingus session, and while I enjoy pleasuring her, it's frustrating for both of us that she's not getting the most pleasure possible. I know exactly where her oris is, but past that I'm lost. I encourage her to be more vocal about what she wants and to direct me, and through that we've seen serious improvement. While I feel we're right on the brink of hitting that big milestone, I'm just looking for any tips/help/advice to help push her over the edge. We would both really appreciate it, thanks everyone!