Anxiety attacks during/after speaking with client

Hello! This is a long note – thank you in advance for taking time to read it and respond.

The Background:
I have one client who has a lot of last-minute requests, which includes asking us for seven proposals in the last three weeks.  The scope of the work often changes after we submit our proposals, so we have done multiple revisions of each proposal – and none have been approved.

She calls me multiple times a week – sometimes multiple times a day – to discuss all the challenges she’s having at her job, and tells me how hard it is for her, and she says that she needs us “because you’re such great partners”, and she’s giving us “priority over other vendors who are also pitching the work.”  She is very manic in her tone, and there is usually a very tight timeline and urgency to her requests.

We make the changes to her specifications, and still nothing gets approved – we just are asked to make more changes, or the entire scope of work changes and we have to do an entirely new proposal.

My business partner thinks our client is “nuts”, that she is calling me “to vent and get free work” and “is using us to get pricing for other vendors”.

And – I have to agree.

The reason I’m reaching out:
The client’s behavior is triggering me in a way that is now causing me anxiety attacks, which I haven’t had in 15 years.  Like Pavlov’s Dog, when I see her name on my phone, the panic sets in.  I’ve tried to do multiple Models, and figure out why she triggers me in this way, but have come up empty.

It didn’t start this way, and I’ve done thought work around her requests before, but she has increased the frequency of her requests and her calls, and it seems to be a cumulative effect over the last three months, because on Friday, this hit a new level for me, and I ended up in crisis and on the phone with a mental health expert.

I do love myself, and I love and value my family (who spent the weekend worried about me). This woman is my client, and I appreciate my clients, but she triggers me in a way a client never has before.

And I don’t want to live this way. I know that I am an amazing person, but she triggers me.

I’ve done several Models, but here’s the one I think is the most accurate:
C – client called and requested additional changes to the proposal
T – I can’t fix her problems no matter how many times I try – I’m worthless
F – anxiety
A – I spin and self-sabotage with self-deprecating thoughts, letting small things drive even worse thoughts and feelings – ending in deep sadness and thoughts of self-harm.
R – I am in crisis and my husband is worried about me and frightened by my behaviour, and it is putting a strain on our relationship.

I know my thoughts about this client aren’t the only thing driving the self-esteem downward spiral, but the extremely negative thinking comes during and at the end of the anxiety attacks that come on when she contacts me. (It’s slightly better if I don’t answer the phone, but it still kicks in.)

I tried an Intentional Model:
C – client called and requested additional changes to the proposal
T – I am not responsible for her solving all her problems
F – calmer (well, less anxious)
A – I listen to what she has to say without worrying about what it means for me, or about me. We can to create a proposal that is what she is asking for to the best of our abilities, but that is all.
R – Empowered

And…that helps a bit, but I can still feel myself panicking.  This didn’t work when I tried it out this morning when she called.

Any suggestions on how to find peace “in the moment” when she calls and not automatically react with panic/anxiety/self doubt?  Intentional thoughts?

And are there resources in SCS for times of crisis?

Thank you!!