How can I let my mom know that I love her but need distance at times?

My mom is very sensitive and at times very emotional. I recently graduated high school and moved out. I still live in the area but i am living on my own and i am attending college. My mom is a professor at the college and i see her alllll the time...It seems like she wants to be with me all the time. She is the best mom in the world! I could not ask for a better mom!! But seeing her everyday makes me feel smothered...i get very aggravated and it puts me in a snappy bad mood..i do not want to be this way towards my mother because she does SO much for me! but i literally can not help myself..my mom is very needy and sensitive and when i start getting aggravated i can tell that it really hurts her feelings.... :( Why is she like this? and what can I do to control my temper and mood swings when she always wants to be with me?? I really hate myself when i hurt her feelings..what to do??