Unsure how to manage blurred boundaries with supportive school staff member

[ThatCoralDeer]

How to approach this?
I'll try and keep it brief but there is obviously significantly more backstory that can be elaborated on it needed.
I am exceptionally socially isolated, no family or friends anymore through severe trauma, subsequent severe depression and a number of significant physical health problems causing permanent disability over the past few years.
Over the past few years I have been supported by a member of staff at my son's school who had gone above and beyond her duties because she's just one of a kind and amazing. She came into our life through her pastoral safeguarding role but has since moved into a different role. I have felt safe confiding in her. But the boundaries have become blurry, I only ever contact her through her work email address (this is all I have, I have never asked for more, she has never offered), yet we now meet for coffee at the end of her working day off the premises. We chat about everyday things, her work, her family (I never ask or probe but she volunteers) and how I am etc. So we're 'friends' but not 'friends'. I feel a constant burden to her, I have said this to her and she tells me I am not and that she would always tell me if I was but I can't shake it. I am hard work because I often get upset/ teary and don't bring anything positive into the relationship.
Last week was a difficult week, after much thought I reached out and asked if we could meet. I just wanted a friendly face and some fresh air/ change of scenery with someone I felt safe with.
I was trying to cheery so as not to burden her but I suppose she saw through that and with gentle probe my tears flowed and wouldn't stop.
And now I feel so guilty again that I bring no positivity or happiness to the relationship and that I'm hard work I want to retreat to give her a break yet I know if I do there is literally no one else for me to turn to.

There is, you need to speak to your gp and ask for mental health support.
have you mentioned any suicidal thoughts to her? I wonder if she’s feeling out of her depth?
who organises these catch ups?

Counsellor for the heavy emotional stuff.

A nice chat and catch-up with this lady. It sounds like you’d benefit from working on your social skills with her, which the above would give you.
But you need professional help for the heavy stuff, because she is starting with good intentions but will get fed up of it sooner or later. And then you’ll feel even worse.

I probably should have said I'm under CMHT, have been for a while (sectioned a few years ago in the aftermath of the trauma for failed suicide attempt, subsequent rTMS and ECT). The meetings are more for a sense of normality outside of formal mental health support but that doesn't mean it's not a lot for someone.

I believe it's her responsibility to back away from this. The staff member has blurred professional boundaries by meeting you outside of work knowing the extent of your need.

I work at a school and would never act in such a familiar way with a parent.
OP, I took it to mean that she had moved role AND school. But if she’s still where your child is, then she shouldn’t be doing this.
If you both carry on with it - I mean, it’s not like we will change your mind! - then maybe insist on buying the coffees so that you are contributing in some way. Might make it feel less one-sided.