Hi Marathon5
My daughter was also 14 when our world changed forever that was 4 years ago. The good part is YOU are still in charge of her treatment until she turns 18. We did it all, multiple IOP, PHPs, residential stay, you name it we got it covered.
Think back to when you were 14, would you want to journal, diary, mindfulness exercises; I know I honestly wouldn't. This is why we needed to think outside of the box with my daughter. She got back into some of HER interests, began painting again, picked up intricate coloring, and got back into nature with her camera. Hiking is a terrific example and we'd do it together with our dogs. Aromatherapy is also being embraced, she loves the way it makes her room smell
Its important to have a discussion with her about her treatment. Maybe she doesn't get along well with the therapist? I know we went thru a number of them until we found 1 SHE liked. Explain its important to participate and work thru the goings on in her life. Art therapy? Girls group? there are options, just need some feedback to find the right match.
Instead of formally writing down in a journal, we talk during dinner about our day, what was pretty cool and what pissed us off, how it made us feel,etc. Before bed, I ask her 1 thing she's grateful for. Initially, she wouldn't take it serious, but then i'd answer and she'd eventually name something

Now its automatic!
As part of my D's discharge from residential, we needed to schedule something together. We started Zumba class and attend class together each week. You may want to try finding something the 2 of you can do together, maybe volunteer in a soup kitchen - this gives them a sense of purpose, something they can be proud of. We trained our dog and she became a Certified Therapy Dog Handler; we visit a nursing home weekly.