You didn't mention your mother's age or circumstances other than that she is visiting for the summer. Is she at an age when dementia may be a factor? People in any of the stages of dementia can be difficult to get along with. Is your mother experiencing difficult financial issues? Having bills to pay and no money to pay them can make anyone grumpy and sadly people take it out on others who may not be responsible for their predicament. They are frustrated and angry and generally take out their unhappiness on whoever is close by or convenient. Try to determine what is causing your mother to behave as she is doing and then think about what you can do to help or improve it. She was there for you when you couldn't help yourself and now it's your turn . . .
I know people get embarrassed when people they're with or related to behave badly, but most of us do not blame the people around them for their behavior. We are all responsible for our own behavior if we are capable of being responsible. I think most people recognize that you can't control your mother's behavior. Look into what is causing her behavior and perhaps you can help her find a solution to more pleasant interactions, or at least a good reason for why she is acting as she is.