If you take her out, that might make it harder/slower to get the treatment she needs. Whilst she is in, it is in their interests to sort out her ongoing treatment, and any tests/scans she needs as quickly as possible, so she can be discharged - and it is much easier to get those tests done.
If she needed another scan, and you’d taken her home, you’d have to wait for her to be sent an outpatient scan appointment, whereas if she is on the ward, they can just send a porter for her. And this would be easier for you and her too.
It may feel like they aren’t hurrying to get her home, but I am sure they are going as quickly as they can, and if you take her home, that could slow down the whole process of diagnosis and treatment.
I know it is difficult and distressing having her in there - for you and for her - but she is in the best place, and a bit of time in hospital now may be beneficial in the longer term, because of a faster diagnosis and establishment of a treatment plan.
I hope she is better, and home, soon.