My mother had a hip replacement and came home from the hospital with delirium. Is this normal or should we head to the ER?

My mother is 69, she had hip replacement 16 days ago. No complications, came home after 2 nights in the hospital. She was put on dilaudid to control her pain, and for 4 or 5 days there were no side effects. Seemingly overnight she's developed delirium; muscle spasms, jerking and twitching, hallucinations, and strange way of speaking. We stopped the medication 3 days ago, but these delirium symptoms are seemingly worse today. There is no cognitive impairment, she's alert to who/ where and all. It seems like one minute she's okay speaking to me, and the next she's slurring her words speaking to someone who isn't there. I'm worried about possible causes, it seems to late to be post operative delirium, and she stopped the pain medicine 72 hours ago. Does anyone else have experience with this. Do we need to head into the ER? Your input is greatly appreciated!