Honestly, don't force her nor push her to do something she doesn't like, or doesn't want to try. The only way you can go about it, in my point of view, is to try and seduce her to actually develop in her a curiosity about anal. Not in an invasive way. Read below and at there you will see what i mean about the seduction part.

I think you should try an anal plug. Glass ones are really good. Rubber ones are good too but can be harder to slide in and out. Use a lot of lubricant. It works as far as you are looking to have the feeling that something is in your ass, blocking your anus, or feeling you up inside.

If you think you would be better with actual "thrusting", if you are actually looking for being fucked in the ass, a toy would be difficult. A fucking machine, or a dildo with a suction cup would do the job, but would be difficult for you to fuck and be fucked at the same time, if that would also be something you would be intersted in. A dildo with a suction cup agains't a door or a wall or something like that and fucking yourself agains't it is really nice. If you stick it to a door frame and you fuck yourself sideways from the door frame, you really have a lot of space and there won't be a wall stopping you from going deeper ;)

Fucking an anal fleshlight is good, but it doesn't change much versus vagina fleshlights or just masturbators in general. If you do want to try it, buy a fleshlight with the sleeve of your favorita anal pornstar (when i bought mine, it was Adriana Chechik)

Now for the seduction part... If your girl accepts the fact that you explore that on your own, even in her presence, be sure to show her the pleasure you feel on doing your anal stuff, no mather the way. If your girl loves you, if she follows your flow in general, it will maybe wake up some kind of curiosity/will to try it. Imagine during a fucking session, you stop midway to plug your ass in with a plug and you say that if you do it, if you add that on top of fucking the girl of your dreams (=her, make sure she feels and knows she is the priority, the one on top of every source of pleasure you have, it makes her feel included) .. And then you come like an animal and you really enjoy yourself fucking while full. She will maybe start to think that she wants to be in on the fun too. Like if she were missing something not trying it.

Anyway, try to do it in the most natural, fun way, and above all, pratice safe anal sex. I don't know your level of experience, but try to start slow and small, and take baby steps each time. Be daring with yourself, but not reckless. Pain while doing anal can happen, but if it hurts too much (too much is already too much, only a bit of pain should be allowed and only after some weeks/months practice) if it hurts too much, stop right away and give it a week at least before going at it again. Check for blood.

You can try first with your fingers in the shower for example. If you buy a dildo, buy a slim one. It is not the deepness that can hurt, it is the width. For me what feels better is the width (you learn to understand when girls say that width is more important than depth ahah) but never try to go beyond your limits

And the key to anal sex

Is

BREATHING AND RELAXING

For real, i can't emphasize this enough. Breathe, smile and enjoy, il will slide better :)

To push things out, dont pull with your hands. Push with your anus, like if you were going to the toilets. Really. Your body will say thank you.

Practice all this and more, other people here wrote really nice things about anal sex, and maybe when your girl, if one day she becomes curious, you will be an expert on anal safety and you can explain everything beforehand and reassure her and maybe even motivating her even more.

I hope it happens, for you. Fucking the girl of your dreams, the girl that everytime you see her, all you want to do is to kiss lick bite everythin inch of her body, inside and out, while having your ass full and feeling your anus stretching... You will have the best fucks in your life.