Slipping Further

Just spent the last 20 minutes trying to persuade and was essentially begging and pleading for my 94 year old dementia and other health ridden foster mom to take her bed time medicine.
She had sundowned earlier than usual today.. and I was met with her saying okay and falling back to sleep, rolling back to her side, not wanting to sit up, telling me multiple times that she isn't on any meds, and that she's not taking it no longer..being confused and telling me that she can't take it if I don't have it with me (I did and tapped the cup multiple times and told her it's in my hand) and her usual abusive insulting behavior towards me resurfaced ..
Telling me that I'm nothing but a pest, repeadly telling me that I'm a pest and I need to leave her alone, etc...
Dementia doesn't stop years and years of abuse..it sometimes amplifies it.

I didn't know what to do. I wish I could've honored her request to the fullest, but I don't have permission and would get in trouble, and possibly foster mom would wind up hospitalized or gone, or her family would kick me out, etc...
It's very difficult watching her slip away further and further each day..

Is there anything different I could do?
Her bedtime medicine is at 8pm, it use to be at 9pm and I moved it earlier. It can't be moved to any earlier, nor any later. I live alone with her. I dilute her meds in water because she can't swallow to well now. She takes meds 4 times a day (5 or 6 if she is ever on antibiotics).
She takes meds daily at breakfast, lunch, dinner, and night. I space them out 3 hours or more between each dosage.
She also is very clumsy and non chalant with the cup that its in and I have to try and catch it before she spills it out.
Anyone else experience this?