Is RV is making her sick ?

I own an rv park in Texas and my 69 year old aunt lives in her rv at the park. She has had diarrhea since Sept. She’s very dizzy from low blood pressure so then she falls. She has vivid hallucinations. She has no other health problems. The 15+ hospital visits in the past 5-6 months have not helped because all her tests come back normal. When she gets really bad, we go BACK to er and they give her iv and get her blood pressure back to normal and send her home. Within 2 days, she’s back to crazy and sick. Could something in the rv cause these life threatening conditions? I welcome any suggestions or thoughts on our dilemma.