Back in 1988, my sister's friend lost control of the car on black ice and it swerved into oncoming traffic on the other side of the highway and got clipped by a semi. Neither of them were wearing their seat belts (which actually saved their lives, BION) and were crunched into a condensed car. My sister drifted in and out of consciousness and was awake for most of the jaw-of-life rescue. Her friend was in a coma for three days from the closed head trauma. Neither of them received any other internal injury and neither of them were bleeding.
My sister was released from the hospital a few hours later, when we could get up there to get her. She stayed in her own clothes the entire time, though her purse and jewelry were put into said plastic hospital bag and were in the room with her. She had a killer headache for about four days and got dizzy easily, but didn't have any bad problems. But, then, she didn't lose consciousness for a long period of time.
Her friend was swept into the ICU, where she was for a couple of months. When she woke up, she couldn't stand because her sense of balance was wonky and her vision was blurred. She was connected to monitors and a ventilator, had IVs and I don't remember what else, but she was wired to pretty much everything in the room. She had to go to PT for a few months to be able to walk again and talk clearly again. It was over a year before she trusted herself behind the wheel of a car.
Losing consciousness (outside of a simple faint) is a big medical deal. Your character is likely to wake in the ICU, where she has a private alcove of a big room with many nurses and staff around, if not with her, and wired to all kinds of things. Sneaking in and out will be harder than just out of a normal room (which is doable). In 1988, my sister and her friend were at a relatively small regional hospital. If this is happening in a bigger city, it's likely to be even more so.
You might want to do a little more research into losing consciousness and closed-head injuries, if you want this to be realistic. If this is a fantasy or she has some Wolverine-like healing factor, well, then you can ignore most of this.