adult ADD/ADHD

We are informally "fostering" a young lady in her early 20s. We suspect that she may have Attention Deficit Disorder. We have known her and her previous landlords for about a year, and it has always been an issue with her to keep her area clean and clutter-free, to remember to do things and do them on time, and she constantly needs reminders which seem to fall on deaf ears half the time. You can be having a conversation with her where you think you both see eye to eye, and the next day you realize that she completely forgot or disregarded what you talked about. It is incredibly frustrating for those who have to live surrounded by her mess. We have no experience with ADD, but an online search showed symptoms that fit a lot of the complaints we have about her. What is the best way to deal with this? What we'd like is for her to clean up after herself, to not leave her belongings strewn all over the house, to remember to do her chores regularly and without having to be reminded, and ideally to start living as if she resides with us, and not as if she is living out of a suitcase - we want her to start taking pride in her belongings and her living area, and to respect her housemates' desire for a clutter-free home and some privacy (she is also on her computer in our living room all the time, forcing us to retreat to a bedroom if we want some privacy, or to bluntly ask her to leave). We'd like her to be better prepared to live at least semi-independently when she moves out, and we get the impression that she has no desire to actually learn how to share household responsibilities with others. We think that if this is a result of ADD, we could know how to better react to the constant reminders and the cleaning up we have to do after her. We've provided her with a written lease agreement that outlines what is expected of her, and we have a printed out sheet of chores everyone needs to do and when, but it seems that words like "clean" and "clutter-free" have absolutely no meaning for her. She knows to "do the dishes" or "dust", but not what it means to "clean your room" or "clean your bathroom". We don't want to come across like we're talking down to her ("to clean your bathroom" means that you do not leave wet towels on the floor, you empty your trash can, you wipe down your mirror and faucet, etc.), but perhaps she needs this sort of specific direction? Any advice would be much appreciated.