@Fairylightsandwine not 100% recovered as it still happens sometimes if I overthink things, but it's much better now.
I can't identify exactly what changed but looking back I can think of a couple of weird things... like I had really short hair with an undercut that I loved but I didn't realise until that point how much I hide behind my hair (reading this makes it sound insane... but it's true). My phobia was linked to my social anxiety and I was stuck following lots of 'rituals' (like OCD behaviour). I accidentally broke a ritual once and when the world didn't fall apart, I realised I didn't need to keep following them.
Also it was so much worse when there was a change to my home / safe space. It always flared up once I'd moved house and felt like I had nowhere to retreat to. Like it was really bad when I was at uni and it flared up again when I moved to another city. I spent lots of time focusing on home comforts and making sure that wherever I was, I was as comfortable as possible.
I also noticed that it calmed down massively once someone at work left (this person was lovely but really outspoken, confident, loud and always misunderstood me, but I had to work really closely with them). I really relaxed then and once my confidence increased, the blushing started to calm down.
Sorry this doesn't sound helpful at all. But two years ago I thought I'd never break free of it, and somehow it just started to fizzle away as I became more confident, relaxed and felt more comfortable in my surroundings. Also, if there's a situation where I'm more prone to it (eg public speaking) I keep myself reeeeally busy up until that point, which helps distract me.
I'm about to start CBT for my anxiety, so if I have an 'aha!' Moment I'll message you and let you know what the real key was x