You don't. Only person that can make the person get help, is themselves. I was in Drug Court, and even with the justice system forcing people into rehab and being sober, a good bit of em still relapsed and pissed hot.
Called being egosyntonic or egodystonic. Does what you think match up with reality? I am BPD and did not always realize I had a problem. I knew my behaviors were not 'normal' but they were a result of everyone else, not me having unhealthy behaviors. Fractured knuckle, punching a brick wall 12 times? Anger issue? I don't have an anger issue. Ask anyone, nobody would say I have an anger issue(True, never blew up around people, always alone). Therapy? lol. YOU need therapy. Took losing a girl, who was almost to perfect for me, ending it the way it ended for something to click. I had to find my own way for therapy to even be an option. Sure, ya could force me into a crisis unit, which my mom did twice, but does not mean I'd leave any different. 4 crisis units, 30 day program, 2 rehabs, 3 months in jail for a felony (Before drug court sentence), homelessness, 2 year Drug Court program and guess what? I am only now seeking help ON MY OWN, and not forced into it. This time, 6 month residential program is MY decision, not someone else's.
What can you do? Be that person she talks to. Don't offer, don't suggest, don't fix. Just listen and empathize. Maybe eventually she will see it. Can sometimes take talking about it before you see the issue and feel a need to seek help. Pushing a person into getting help, isn't talking about it. Often ends up having the opposite effect, pushin them away from help.
"Could you drive me to X?"
"Sure, np, wanna grab some lunch after?"..."Hey, d'ya hear that bus that caught on fire on campus? Crazy shit."
Ever decides to get help, likely already nervous as all hell, feelin all kinds of ways. Make em comfortable, don't draw attention to it, increasing the nervousness and shit. Unless they want you to. Be the kind of person that is there for her when she decides she needs help, judgment-free, pressure-free. Can either do what you can for her, or drop her to avoid any possible future pain. It doesn't make you a bad person if you can't handle it. Not required to stay and deal with it. Not everyone can handle it.
I had a friend that would talk about wanting to lose weight and get in shape. I just listened, said "I feel ya" and let him talk. Randomly, ask him if he wants to play some tennis, heard he played when he was younger. Always been interested in playing, but never anyone to play with. Made it about me wanting to try out tennis, not about his weight or lack of fitness. He was doing me a favor playing tennis, not the other way around. He whoops my ass, cause I'd never played before and he played as a kid. I pick sports up quickly, and start to win. Bout 50/50 whod win. Start to talk shit, playfully, like friends do in sports. Becomes competitive, start to play a bunch.
At no point did I bring up his weight, try to tell him what to do or turn it into something other than a fun time. Just tricked him with exercise disguised as fun times and doing it for me, not him. And he started that habit of exercise he talked about, without really even realizing it. No dread, no anxiety, no fears.