Mom is losing about 5-6 pounds a month. How long can the body go on losing weight?

Hi I have been on here for the last 4 years..everything I have read and y’all answer my questions have been very helpful..thanks..but hope y’all can help again..my mom has been on stage 7 for 1 1/2 years..she is also on hospice for 2 years..she has been eating about 30 to 40 percent of her meals a day..drinks very little..she has loss 20 pounds in the last 2 months..I have tried everything so far and bring in things that she likes to eat and has no interest in now...my question is she is losing from 4-8 pounds a mth..she is at 116..her heart and oxygen and blood pressure is good..but all that hospice tells me it’s the process..so how long can your body go on losing this weight..before the organs can just take her life..one great thing is that she is in no pain..thanks..