For feeling upset that my aunt involved my estranged parents after I asked for help?

If you didn't want your dad to know, you shouldn't have agreed to your aunt speaking to your mum. In this area, even a room in a house share costs around £850 a month so if my nephew needed help with rent, I wouldn't be able to help out with the whole amount. You agreed for your aunt to speak to your mum - why? Your OP states that you are estranged from your parents so why would you want either of them to be inviting your financial issues? It's also unreasonable to expect your mum to keep this from your dad, partly because any money forthcoming is likely to be from the family pot partly because as her husband, she may choose to share this with him.
Unfortunately OP, I think this is all on you, either you are estranged or you're not. If you are, that means no contact at all.

I see why you are NC with everybody…

I think you can’t expect a married couple to keep things from each other.

Then who will she ask for money?

OP broke the boundary and cannot see the irony of stipulating NC and then reaching out for money (to a close family member). Entitled bdhaviour. OP should step away. Why didn't OP put aside savings when she was working.

I have read the post properly and it seems that you were expecting your aunt to talk to your mum alone - but she talked about you to your mum and dad together.

I can understand that you may be upset about that ( as you are entitled to be ) but did you make it absolutely clear that you didn’t want your dad involved?

Im a bit confused about the borrowing money from your parents situation? I know you said that you don’t/didnt expect them to bail you out - so what was the point in even involving them?

Also just to add - it’s really irritating when posters get all defensive and do the whole “ oh you don’t know my life/what I’ve been through etc…

No, we don’t! You are just talking about an issue you currently have and it’s almost impossible for anyone to give you the exact right answer.

so they could work together to help. I agreed she could speak to my mum

Have read your OP.
You went against your own boundaries.
You are NC with your mum but agreed your aunt could contact her.
I am sure your mum would wish to help you but if neither her nor her sister have the cash needed then your mum would need your dad's help (if in a joint account). The offer of you moving back is an alternative if the shortfall does not fix things or LL serves you notice for defaulting.
You cannot be blaming aunt or mum for that.
You say for all to read your OP but it reads that you are happy to take money from your mum as long as dad does not know. What else did you think "work together to help" would mean.
You may see her as an enabler but your poor mum.

@ByAmberRobin It sounds like a very difficult situation for you.

I don’t think anyone can set a boundary that other people won’t communicate with whomever they choose to communicate with, the boundary is about who you will communicate with.

Your aunt is never going to fully understand the complexity of your relationship with your parents and she is probably most loyal to your mother as the sibling relationship is typically stronger than a niece-aunt relationship. You have to have a relationship with her that respects that if that is the reality of your situation.

Your boundary is probably necessary with your aunt.

Is there anywhere else you can turn? Are there any other practical options you are missing. There was a tonne of extremely serious abuse in my family growing up, no matter the circumstances ever, I could never ever turn to them for support because the cost of that support would end up being enormous. That group of people simply do not have that normal family capacity.

Accepting that means I have to look in other directions when life throws its inevitable curveballs out way. It is incredibly sad that when you are in this situation you do nearly need to become hyper independent but often that is necessary.

Everyone read your post, which included the information that you agreed that your aunt could contact your mother.

Exactly. The OP agreed that the aunt could tell her mum so that her mum and the aunt could "work together to help".

Given that the OP is estranged from her mum, what kind of help would her mum have been able to offer if not financial?

We did read your post. You agreed for your aunt to speak to your mum. So why agree to that if you didn’t want them involved?

But the OP agreed in advance that the aunt could tell her mother. That wasn’t the aunt going behind her back.

So why did you agree that your aunt could contact your mum? What other reason would there have been for involving her, given that you are NC in any case?

We did read the post. Your aunt contacted your mum with your agreement and you seemingly would have been happy to accept money from your mum if it had been forthcoming.

I find that somewhat surprising from someone who has apparently taken the decision to go NC with her parents.

Aunt got OP’s permission before speaking to mum.

aunt may feel weird going behind sister’s back even if she had the money

If you were my niece I'd just have given you the money and not told either of your parents. A pity your Aunt did not/could not have done that.

Of course anything you tell your mum will be told to your dad - and it is unreasonable of you to expect or ask otherwise. You sound very young. It is also unreasonable of you to cut your parents off and then expect them to bail you out. You can't have it both ways. If you are standing on your own two feet, as you should be at your age (unless there is a backstory of disability) then don't cut off your parents and then expect them to help - sort it out yourself. If you wish to rely on them at difficult times in your life then you need to work on repairing your relationship with them.

You can't expect to be bailed out by someone youre nc with.

The OP is relying upon fammmmmlllllllllllyyyy to pay her rent.

How can you be 'no contact', but expect no strings financial assistance when it suits you?

You don’t know what the conversation was between your aunt and mum. Your dad has found out, YABU to think he wouldn’t!

You can't expect your mum to keep secrets from your dad. You've been very naive and, the way you have written it, quite controlling. (Although I appreciate there may be a lot of background to this that we're not aware of).

Are you sure your aunt told your dad? It could be that your she spoke only to your mum and your mum told your dad.

Also, if you are NC with your parents, why are you willing to take money off them?