how possible is it for a person date a recovering heroine addict?

It's possible, but not likely.

Do you want to help her either way?

they way you think when you are taking drugs drastically changes when you sober up.
The only thing that will tell is time unfortunately.

She may still feel the same about YOU , but you may not feel the same about her. She will be a different person now.. so, if it is worth it to you, hang out and see who she will be now.
If not, count your losses and leave quickly.

I guess that wouldn't be the worst thing in the world for a person to do, stick out a hand to someone who needs one. But there are downsides to this for both of you and those are things that only you two can figure out.

I wish you both oodles and oodles of luck and my best wishes.

It's possible. My sister's Ex has a sister who used to be a heroin addict. At the time she decided to quit, she had a permanent boyfriend. She's been clean for at least five years now, and still in the same relation.

Don't ask me how they made it work -- I didn't know either of them in person -- but I know that the answer to your question is, "it's possible".