L5 S1 grade 1 slippage and IBS. Out to!

Hello My mother is suffering from L5 S1 grade one slippage since 2019. In 2019 We had visited spine specialist who has given medicine and excercise and she was comfortable to walk wearing bealt occasionally. Since last 9 months she is suffering from stomach issue of diarrhea,  feels stomach is full after eating small meal and need to  empty stomach after eating. we have visited gastroenterologist who gave medicine like  post which it's in control along with diet changes. Blood tests and stool reports are normal. She lost around 4 kg of weight  during 4 months which is stable now. There is also muscle loss observed At present she isn't able to walk or sit for more than 5 mins . Orthopaedic has given medicines like maxgalin and nice. We are confused that stomach problem is not resolved even after taking medicine for 4 months and back problem has increased we are confused whether we should treat L5 S1 problem first or stomach ? Are these related ..which specialist should we reach out to