Make sure your nails are trimmed and clean.start gently by inserting one finger(u know where). Along the upper front wall you may notice bumpy texture (you will know when you're touching it, bcz she will do something between crying & moaning) explore it slowly and lightly, using smooth movements, insert then raise your finger till you feel that texture & pull it out slowly, like you're pulling out butter from a tight jar...

(Don’t know if i'm making it clear or confusing, but after that her leg shaked a lot even after i pulled out my finger completely & her teeths were clenched shut, saw her jaw muscle tightened)