Point out that until you go to hell, you will continue be that good person she has discovered until you die.
Therefore, in this real world, you are acquitted of all charges.
Later, ask her if she believes that devout Samkhya Hindus will go to hell? If she thinks they will be "saved", point out that they have no belief in a god. If she thinks they will be damned, ask her if she approves of yoga, which they invented.
Either way, it should help her to start questioning her ingrained beliefs.

You did GREAT, and I would do the same thing as you've been doing. Who knows, perhaps the day will come along when she will actually THINK of the conversations you've been having and perhaps a light will blink in her world !!!!!!

If you like her ...talk to her, if you dont, don't !

Wait

Nicely argued. You're a god friend.

If you are friends, I would continue to be supportive of her in her quest to honor fact over belief, if she is seeking change that is.

How important is it to feel needed by her? ... I remember once a guy called me an asshole, not on religious but on ideological grounds. I asked him whether would rescind from this insult. "NO" he said emphatically. "Great," I replied, so I don't have to pretend to respect you.
Why don't you challenge her on the specifics of hell? Temperatures range, fuel type and consumption etc. and what materials are being used to insulate Heaven from Hell.

Telling an atheist they will go to hell is about as scary as a warning about the possibility of being gored to death by unicorns. Take a light hearted approach to any of her outbursts, walk away laughing & shaking your head, & she may get the message that she's wasting her time telling you fairy stories. If not, she doesn't deserve your friendship.

Knowing only what I read into your post, you showed her kindness even when she attacked you. This is what a true Christian SHOULD do but obviously she is not getting this from her christian peers. In my opinion, continue to be kind and walk away when she turns on you. If she doesn't come to see what she is doing, walk away and rest easy.

I'd block her number like I did for all of my ex-in-laws.

Just be nice and be honest, I guess.

I'd ignore her and find another friend. She is obviously been brainwashed and conditioned nearly to death. The only way she will find out she is wrong will be to die! Tell her to send you a postcard from "Heaven" when she does!