You are not alone with this problem. My dd graduated in 2023 and has only just got a job that in any way uses her degree (modern languages) and my ds graduated in 2024 and has just got a job for which his degree helped, but not really in the field he wanted, and he has had to move 400 miles away.
I haven't read the whole thread, but I am guessing the usual suggestions have been made. What helped for my dd was signing up to a temping agency and doing minimum wage admin work until her recent job offer came along. She clearly had a good CV as she got plenty of interviews but they never resulted in a job. She was always '2nd on the list', or so the recruiters said. Right now, for your dd, any job experience is better than none. In my experience, and that of my dd, the best way to get that is through a temping agency. You often don't even have to interview for the role, so if shyness is holding her back, that might be a bonus.
Can she drive and does she have access to a car? Might not be that important in big cities, but it is a useful skill anyway, and it helps to not have to narrow the search down to major cities. Edited to add: I see now she can't drive. Definitely encourage her to learn. It will boost her confidence and get her out of the house if nothing else.
Would a bit of travel be possible? If she can afford it, or if you can, going abroad just travelling - gaining experiences, gaining confidence, practicing her language skills in real life situations, not specifically looking for work - might take the pressure off her and allow her some much needed release. It also gives her something to talk about in interviews. I know that sounds daft, but my shy dd is a big traveller and was able to establish a rapport with interviewers when talking about her travels.
The other thing my dd did was attend evening classes (online) extending her language knowledge. At the moment, she hasn't been able to build on her skills in that department, but the intention is she will do so one day.
Sorry if none of the above is helpful. I do feel for her, and you. I am so relieved that things have finally come good for my 2, but it has literally only happened in the last month and so it is still fresh in my mind how utterly bleak and hopeless it can seem day in day out with nothing to look forward to. You are not alone.