Why Didn't Jennie Stop Telly At The End?

When she gets to the apartment and sees Telly having sex with Darcy, why doesn't she stop him? It didn't seem like it was too late to me.

I'm no expert on HIV but I always assumed in order for a guy to transmit HIV to a woman he usually has to ejaculate inside her? Or even if it's not the only way I assumed it was the most likely way. I know there is pre-ejaculate but guys don't always release that so it would have been worthwhile to stop him in case it wasn't too late. I assume its also possible if there are small tears in the penis but, again, that's not always a sure thing in sex.

So why didn't she stop him? It seems like a very messed up thing to do to allow Darcy to get exposed to HIV.