D.D.
Methotrexate is a cancer drug so the warnings you are reading are for much higher dosages than your mom will be taking. I've been on it for several years for treatment of psoriatic arthritis with few problems. Because the methotrexate came take several months to show if it's working or not, physicians usually give something for the pain or steroids to help with the swelling. :
I'll pm you with tips on taking the methotrexate so it'll reduce the side effects until mom gets use to it.