It's been a long ride for her, she's not happy with the way she looks but she hasn't been doing things that will help achieve her goals. She's going to therapy, but doesn't do much with it. 

Maybe she just doesn't want to do anything now (lack of motivation aka laziness), but with the way things are going, she's going to dig herself in a hole. 

What can I do as a boyfriend motivate her to do what's right for her body? Keep in mind that she has depression, anxiety, ADD, ADHD. I always walk on thin ice around this subject because of her past personal issues so I feel stuck. She can never stick to a routine so it's very difficult.

The goal is to lose weight healthily. She's 5'2" ~ 155 lbs. Her end goal is to be around 100-110 lbs. 

Suggesting new diet is probably not going to help.