I have researched. I started by researching different types of memory losses. I looked at a list, read a bit about them, then researched some that seemed promising(but didn't work, or if they did, I didn't understand that). I also googled in my question a few different ways, though that did not work.
The types of memory loss that I thought were promising are vascular dementia(It is more of a forgetfulness, losing small memories I believe...though I felt like I was missing something with that, so maybe it does work?), transient global amnesia(that did not work as people gain their memories back. Always), and strokes. Strokes would probably work, though I would rather use something other than that. It is not the area I was intending for the character.
My story is set in modern day England, 2013, and my character is in her twenties. The setting is a hospital, mostly. The other MC has Schizophrenia, and his form is mostly delusions.