It can be very distressing to be accused of things you aren’t doing. The best thing you can do is not to argue with your loved one or try to get them to see the reality of the situation. They aren’t able to understand.
If they are accusing you of stealing the same objects over and over, consider having them in a place where you always know where they are. You might also write a note that say where the items are kept so that you can show your loved one—this isn’t to make them feel wrong, but to reassure them.
Sometimes offering a simple explanation as to why she can’t find them without trying to convince that they are wrong is helpful. Distraction to a new activity can also help.