from my experience with my gf, she wont get high if i poke my
finger in and out. She will get high when i use my middle finger to
rub her G spot. The exact location may not be the same for every
girl, so u can try it and ask her to tell u where is the point she
feel most sensitive.
one thing is, dont rush, start with slow rub, get her in the mood
then increase the speed gradually.
she cant be too shy, she must at least dare to tell you what she
wants, or else she cant get high.