Should I decrease the rent I pay my mother?

Ok. Here is my situation. I am 32 and having been renting the in-law apartment in my mothers house for the past four years. My 7 yrs old son lives with me. I have been paying her $800 / mo for rent, utilities included. In the main house she live with my two brothers, ages 23 and 19. My parents have been divorced for four years and this is the house we grew up in. My great grandfather on my father's side built the house and four generations have been raised in this house (may be irrelevant, but whatever). 3 weeks ago my mother but the house up for sale. She told my brothers and I the night before the sign went up. Her reason is because she want to live in a one bedroom condo and does not want the maintenance of a house. I understand and respect her reasons. However she then went about saying that she can't let my brothers "stand in her way anymore" and when I asked what they were gonna do she said it is "not her problem" . Long story short...I don't make much money nor have much in savings and I will be in need of a new car in the near future. I have asked her to lower my rent while the house is on the market so I could save up for moving expenses and a down paymt on a car and she said no. My father and brothers think I should just stop paying her. I feel bad doing that as I still use utilities. Should I just tell her that I can only afford to give her $400 end of discussion? Also, makes a very decent salary and my brothers also pay a small rent between $200-300 per mo. She is not selling the house because she can't afford it anymore.