My advice would be to lead by example, just like you have been doing. Try new things, such as:
-Starting the kiss slowly, don't go in w/ the tongue first.
-Progress to brushing her lips w/ your tongue.
-Gently slide your tongue in, keep it smooth. !No Harpoon Kisses ! lol
-Make circles with it like you said you did.
-Practice makes perfect! Just enjoy the moment, and don't make it too complicated.
Also, Maybe she just likes what she has been doing, and doesn't feel the need to change her style. If this is the case, let her continue doing what she likes. If it is a real problem, tell her how you feel about the situation, and see if she is willing to try new ways of kissing.
Good luck,
Hope this helps!