best thing you could probably do is get her to msturbate in front of you and watch what she does, what excites her, what makes her jump when she touches a certain spot. It's not just about sticking your fingers up her clit, it's about hwo gentle you do it, and where else you rub on the outside at the same time, how far you penetrate her, and try licking her at the same time as well. You may find she enjoys stimulation more on the outside with your tongue and hands. How did you go about it?
You guys are still young and have a lot to experience first, the most important thing is communication between the two of you, not being scared to show what you don;t know or understand, and seek others thoughts as well like you did on here, which is great.