If she's a true friend and you two are close, make an appointment for her and drive her to the doctor. I know for me, when it finally got to the point I couldn't take it anymore, I wanted to see a dr. but was too embarrassed and hesitant to actually set up an appointment myself and my husband ended up having to do it. And, I am truly glad he did because now, though years later, I don't have to take my medication anymore. I haven't used any anti-depressants in roughly a year and I've been absolutely fine even with all the stress I've been under.
If that doesn't work, I don't know that there is much more you can do that you haven't already. A person has to be willing to seek and receive help, stick with their treatment, keep in contact with their doctor, and, most importantly, tell their doctor if the medication isn't helping or causing negative side effects. Not all meds work the same for everyone and sometimes it's trial and error until the proper medicine is found.
--The member formerly known as Demonica
"You must be the change you wish to see in the world."
- Mahatma Gandhi