She's so freakin lucky she made it back!!! I've been watching Dateline "To Catch A Predator" and I can't help remembering my stupid days...when I was 14 I used to have personal meetings with guys I met online (all older) in the dead of night. I thought I was smart by leaving their screen name and phone number on a note under my pillow. I'm so glad God protected me and that I was FAT back then, cause if I had been a cute little girl and God hadn't been looking after me I don't know if I'd still be here today. Online predators (not just pedophiles) are a VERY real threat, and she needs to get help. I understand not liking her, but she IS still a human, just like you said. She doesn't think the murder/rape stories you hear in the news would ever happen to her, and even though they might not there's still a real risk.
If she wasn't doing the stuff that she's doing, if she wasn't this type of person, do you think you and her would get long? Is this the only thing that keeps the two of you divided? She does need help....I wonder what would happen if her husband found out about all this...would he ditch her or help her? At least, in the VERY least, talk to her about leaving the phone number, screen name, time/location of meeting, and how long she's planning to be gone with someone she trusts, even if it's you. Have her schedule check in times, she's gotta call in every X number of hours to confirm that she's okay. Those little precautions can make all the difference, and she'll soon be regretting her decision to fool around online if she ends up in a ditch somewhere....
Good luck, and bless you for being concerned....she may be old, but even old people need someone to look after them sometimes....