Some of your elements move to the monitoring system and copy what signals it is recording, then start playing them back so when she dies no-one will come in and interrupt you. The rest of you crawls onto her body and waits.
It doesn't take long. Soon her signals slow, waver, then her heart beat fails. The monitoring equipment still shows her as healthy, so you should not be harassed. Now you move, your Nanocells burrowing in between individual skin cells of her, moving inside her without any real damage to her body. Once all of you is within her you spread out and begin the repair work. This will take some considerable time!
At first you analyze her internal structure and organs, trying to determine exactly what needs to be done. After this you set up a group of your Nanocells around her heart and start it going artificially by squeezing it rhythmically. The heart is still not functional, but outside sensors would show it was, and the body would seem to be alive. Blood is being pumped and you attempt to get the cells working again.
You begin in the vital organs, heart, lungs, liver, stomach and intestines. Slowly you repair obvious damage, then stumble on some odd cellular anomalies. You believe she was suffering from cancer. The cancerous cells are spread throughout her body, but one by one you eliminate them directly, high voltage arcs burning the cells out without damaging adjacent tissue. It does leave a lot of repair work to do, but the cancer is gone inside of two hours.
Repairing the rest of the body is slow and takes over a day, but eventually it is capable of operating on it's own and you remove your elements from around her heart and let it beat normally. The brain is severely damaged from lack of oxygen and other problems from the hour it went without the heart working, however you start by reconfiguring it, setting up the remaining nerve ganglia to start to grow and rebuild. The brain will serve as a form of hard drive for your mind which will stay in your Nanocell network. Over half of those cells migrate to the brain now, helping get things going. It seems to work well.
Finally, after two days of effort you integrate fully with the body and awaken, opening your eyes.
"This... is... odd." you manage awkwardly, but manage to sit up.
You don't think interacting with the doctors would be a good idea so detach the monitoring system, still rigged to show your life signs without you being connected, and attempt to open the window. It seem to be securely locked, but some of your Nanocells migrate out from your hands and into the lock. In less than a minute you have eaten the metal of the lock enough that it falls apart and allows you to open the window. It also forms a good metal base to build more Nanocells, putting you up to 120,000. More than enough.
Still wearing the backless hospital gown you climb awkwardly through the window and leave the hospital parking lot. Once you are well clear you ponder what to do.