Pet Sitter - Full-time / Part-time

2 of our cats are rescue brothers (same litter) and are 5 years old. Our other cat is also a rescue, snd is just a bit over 1-year-old. She has had chronic diarrhea since we got her, we have put her on 2 different antibiotics to no avail, and recently did an ultrasound which showed enlarged lymph nodes on her intestines. We are at the point now where we have to decide whether or not to do a rather invasive stomach biopsy to definitively determine whether she has cancer, or just treat her with steroids and possibly B12 shots. We are waiting for some more info from our vet, to help us make this big decision. We just want her to be happy and pain free, so these decisions are pretty tough.