I started taking benzodiazepines when I was 14, I took them for 9 years, at least 6mg of clonazepam every day for ~6 years. I quit 2 years ago, my life now is not a fairy tale at all, I've got tons of problems, my social life is none, ibut it's not really much related to my past benzodiazepine use but rather a consequence of isolating myself and avoiding bonds with people. Symptoms that I know are due to long-term benzodiazepine dependence are very bad sleep and dissociative episodes coming back every now and then. However, after I quit benzodiazepines, my memory has improved substantially and I got rid of social anxiety, benzodiazepines eventually made me more anxious than I was when I started taking them. If she is to quit benzodiazepines, then there will be no better time than now, it's very likely that she no longer experiences much positive effects and she definitely experiences a lot of negative ones, and bad news is that they will keep worsening. If she decides to stay on them for life, then that's a very unfavourable compromise with life if you ask me.
Edit: Just read about heroin...

In this case if she is to quit benzodiazepines, she probably first needs to get stable on a maintenance drug. I can't see it working out otherwise. Getting off benzodiazepines after years of use at such doses is truly a nightmare, if you happen to withdraw from heroin and Xanax at the same time, it's truly one big hell of a hell.