Advice please? possible trigger maybe

It's normal for her to revert back to the sadness sometimes, especially if you all just started to work on what is troubling her. The twists and turns are going to come whenever you try to get to the roots of any issue, so just be patient . Reassurance and encouragement is very helpful too! It's always good to feel welcome and loved, even if you are troubled, as I've come to learn with my others. Be the shoulder for her to lean on and soon enough she will trust herself and you as well, and know that what is on her mind doesn't have to feel like a burden.