Mentorship Advice

[MessedupMentor]

NC for this as I'm not sure how revealing it is or if I'm even coming to the right place for advice.
I really enjoy my job and have made some good progress, I work in a lovely team, due to company expansion my colleague and I now trialling a joint senior role, it's going really we and work really well together and have learnt a lot.
The issue I have is that I am currently mentoring a junior colleague and really struggling to motivate her. She's been with the company about 6 months and I know that this can be a bit of a crunch time in our role, the work gets harder and the expectations become higher. She seems to have hit this stage and despite my best efforts she's facing this with a really negative attitude.
I've tried the nice easy going approach, which is my usual way, and she seems to take this as her que to sit back and do less.
I've tried the watching everything she does approach and this stresses her out more.
I've tried being hard on her and she just got really upset and I felt awful.
We had a clear the air chat and she did say there were aspects of her job she was unhappy with which I have provided extra support and training to cover.
We have informal team meetings every week which she does not contribute to even when asked her opinion she has little to say, I always make myself available for support and help but she seems to be shutting down and going further into her shell.
How do I get the best out of her, she's a bright, intelligent and lovely person and I feel like I'm failing her?