you asked if she truly needed to be alone to work on her recovery....in short, yes. addiction is a mean hombre and heroin/opiate addiction is insanely hard to overcome. the body SCREAMS for the drug, the mind SCREAMS for the drug - be the same if you dove underwater, and then tried to stay there for two minutes....your lungs would soon SCREAM for air. and you would have no choice but to kick hard for the surface.
trying to learn the tools you need to beat that kind of affliction in a week, or a month and then for the REST OF YOUR LIFE takes absolute attention. complete devotion. you cannot waiver.....not for a minute, as every addict in recovery is exactly and precisely ONE bad decision away from falling back in to active addiction. that doesn't leave much. people in early recovery don't know their @ss from a hole in the ground....for a while. their lives had been centered around drugs...getting drugs, using drugs, finding ways to pay for drugs. cuz drugs ain't cheap and drugs ain't free.
so here is this young 24 year old burdened with this monster gorilla on her shoulder. if she doesn't kick this now, she's looking at the progression of addiction....shaping the direction of her life.
you can't fix this. you were a presence in her life for two years, and you basically had NO impact on HER addiction. any more than you could influence a disease or illness. WE cannot get them WELL and then KEEP them that way. it's noble to think so, but it is unrealistic. her addiction was there long before you showed up at the bar.
she is IN rehab. that's her best chance. what she does after she gets out will dictate whether she will be successful at staying clean. often addicts have to ruthlessly change their playmates, playgrounds and playthings.
it's life or eventual death for the addict. yeah it IS that serious.
i'm a former crack addict (among other things). I didn't start smoking crack til I was in my 40s. it got me in less than 3 months, after approximately 12 using events. GOT ME. and then went the next 4.5 years of my life trying to stop. it got worse, before it got better. my partner hank who "introduced" me to crack had been addicted to coke/crack for 20 something years. I got ready to stop before he did. so I had to make the decision and then put it into action to NOT USE AGAIN NO MATTER WHAT while my partner was not yet onboard with that idea. I didn't do rehab, I didn't go to meetings (altho I had many years before) and my support system was online.
eventually hank came around and we are both today coming up on 8 years clean. he came to his decision on his own....I sure as hell couldn't MAKE him stop, LOVE him into stopping, HELP him stop.
the big difference between diseases like diabetes or cancer vs addiction is that if the addict simply QUITS for good, the disease goes into remission. we can't just change our mind and make cancer go away. anymore than not eating sugar products fixes diabetes. nor can a cancer patient in remission completely prevent the disease from returning. but an addict can....with a daily reprieve based on the choices one makes.