AIBU To Say No

Argh, wretched automatic typing. Forgive horrible grammar errors etc etc etc 😂

Unless you can afford the risk you have to say no, unpaid rent can be thousands before someone is evicted and as guarantor the landlord could come after you for unpaid rent. X

If your DD can’t get a flat because of them insisting on a guarantor, then maybe she could look at a house of multiple occupation . They very have en suite rooms and are cheaper than a flat and at least she would have a roof over her head .

Deep down they are still our babies!

Say yes
I know this is against what everyone else is writing. But you can have a good credit rating and still need a a guarantor.
She needs somewhere to live. It’s so bad for health to be sofa surfing. I imagine she has always payed her rent. Many people who have are homeless.
It’s not their fault they homeless.
If your homeless your so vulnerable. It can happen to anyone and it will effect your physical and mental health
Help your daughter

The OP has explained that she can’t afford to lose the money she might be called on to pay. On what basis do you ‘imagine’ the daughter has always paid her rent? She has a chequered employment history and evidently no references to satisfy a landlord. Don’t guilt trip the OP, who has rightly already said No. Your ‘advice’ is reckless in the extreme.

No, a million times no.

Moonwatcher 1904 - you did the right thing. Your daughter may have ADHD but that doesn't preclude her from getting a job that brings her a salary/wage. And it doesn't exonerate her from sending nasty messages or kicking off when things don't go her way. I have every sympathy with people who are neurodivergent, I see many as clients, but neurodivergence is no excuse for emotional blackmail and if you play into that your other daughter will hold that against you. Maybe you could suggest to your daughter that she rents a room in a larger house and that might not require a big deposit upfront. If she doesn't want to consider that then it's obvious that she wants to live above her means - always a problem for those who are called upon to make that happen. I'm not being unsupportive here but it does seem as though you've been there for her before and for quite a long time, and she's come to expect this.

Just be honest and tell her you are not in a financial postion to
be able to do that.

It's not unreasonable to say 'no', though it feels upsetting to do so.
Better 'no' than 'yes' and putting your own security at risk.