My Girlfreinds in pain when i fingure her ?

i have mentioned fingurin her but she says she dosent like it because the last time she done it what was her first time it hurt... why dont you try it on yourself a few times to get use to it and she said it makes me feel sick doin it to myself. How can i make it less painfull when i perfrom this and will it get less painful for her after a few more times ?