<human>: Could you distill the essence of the text into 1-3 sentences?

My GF:20 and I (M:20)have been dating for 1.5 years, everything is fine in our relationship but I really am concerned with her relationship with her Mom and myself being dragged into it. 

Her Mom is extremely overbearing, needs to be in constant contact and etc. This amongst drives her absolutely insane but the main issue is her firm belief that my GF is terminally ill. I was always told about how her mom insisted on frequent bloodtests and checkups to the doctor and it is to the point where my GF pretty much avoids any conversation with her Mom at the fear of having the topic come up. GF's Mom called me hysterically crying saying she looks sick because of dark rings around her eyes(Early AM college classes/studying), she was begging me to convince GF to take another blood test. 

I am sympathetic to  the woman because I know she lost a sister to leukemia at a young age but this can't be healthy and am worried about the stress it puts in my SO. Gfs mom already sees a therapist for issues from a divorce. Have any suggestions on how to handle this type of behavior?
<bot>: GF's mom is an overbearing hypochondriac who is convinced my girlfriend has cancer even after multiple blood tests prove she doesn't.