I suspect that you're not telling us the whole story. My guess is that she really doesn't want to at all, and you're trying to bully her into it. . Far be it from me to render judgment, but IMO only a pervert would want to do anal sex, or to receive it.

Its all about the feeling that is between you two. If you reasure her everyday that she can feel uninhibited, she will want to try everything with you. There are couple of forms of anal sex and penetration is just one of them. Do some research.

Try telling her that you think she'd really like it (so she knows its not just for your pleasure) and reassure her that you'll take it slow at first and if she wants to stop you will. Be warned however, its not always just the idea of it thats a problem. I have wanted to try anal with my boyfriend a few different times. Some stimulation is grrrrrreat, but full on penetration hurts and makes me want to poo. If it doesn't feel good, dont expect her to want to do it, that's just being selfish. Good luck and if she poops on your dick, you better not throw up on her!

You want to have anal sex but she doesn't - period. If she's not up for it then don't push her into it. Instead see if she likes the sensation of her anus being tickled from inside her vagina. This is what got me onto the whole idea of it. Its clean (one major fear is being dirty) and its really pleasurable but warn her about what you are going to do because it really feels like you have a finger up her butt! If she enjoys it then you can try to see if she likes external stimulation of the anal sphyncter. Wet you finger or lick her anus whichever but it has to be lubricated. She also has to feel really clean so its a must that she agrees to this. Without being graphic if she needs a poo then you'll get a finger full of poo if you try anything but if shes ok then you will be alright. Have some babywipes and a bin to hand as well (my preference!) Its not for all the time - and you really do have to pick your moments carefully. If she does agree to any penetration you have to penetrate her with your finger first but use lubricant (not spit) and lots of it. If shes tense it will hurt. She has to be completely relaxed in order not to feel the 'sting' and it does hurt! To completely relax the anal sphycters try telling her to push a little, once she knows what that sensation is and how much easier it feels she will be able to relax more and enjoy it. You have to be completely aware of her feelings at all times and if shes uncomfortable don't force her.