That is a difficult situation. If I were wealthy and one of my siblings couldn't afford dental work, I'd pay for it in a heartbeat.

That being said, it's ultimately your teeth, and therefore your responsibility, to come up with the cash. Although it would certainly be a nice gesture from her, she owes you nothing.

I am curious as to why your teeth are in such rough shape as well. If it was a case of you just not taking care of them properly, then that is your fault and you need to take responsibility for that.

My suggestion? Start saving what you are able, and don't expect help from your sibling. I wish you the best.