Am I Wrong??

 So, here's the background.  Joey had a kidney transplant at 18.  I was always told that they didn't know why they failed, and that they have no idea what even started it.  So Joey has been paranoid about Marlow's kidneys.  Understandable.  At her one year check up I asked our family doctor, who was also the doctor to discover Joey was in renal failure(and not his family doc at the time) about getting Marlow tested.  He told me that the reason Joey's kidneys failed was because he had an undiagnosed and untreated bout with strep throat.  Apparentley the only reason strep throat is treated is because if left alone it can cause an infection in the body and cause organs to shut down.
 
So yesterday we were out for supper with his parent's and his mom asked me about getting Mar's kidneys checked.  I told her what the doc told me.  That Joey's wasn't hereditary and that unless there is signs showing that Marlow's kidney's were in distress there was no need to go poking her. 
 
Well, she flew off the handle at me!  She claimed he was lying.  That I was insinuating that she didn't take care of her children...that I thought she was a bad mother and that she would let strep throat go without a doctor's visit.  She claimed that the pediatrician they went to as a kid has all the records and that they were there as soon as they so much as coughed.  She told me that I was a bad mother for not pushing she get tested.  That I didn't love my daughter obviously or else I wouldn't play games with her life.
 
She had me in tears.  In the end I told Joey I was going to wait in the car.  He quickly settled up in the restaraunt and brought Marlow out.  He then told me that he understood where his mother was coming from.  That he was also worried about Mar's kidneys.  I get that, but did that mean she could yell at me in a public place about being a bad mother??? 
 
I don't know if what I'm doing is right anymore.  One of the things she snapped on me about was if I took her to their old family pedi(who I do visit on occasion but he is incredibly overbooked) that he would order the blood work.  Joey is worried about her kidneys, and he's worried about what I am going to do next regarding his mother, and he's worried just plain and simple.  I have no idea what he said to his mom after I left, but his dad came out right before we drove away to see if I was alright. 
 
I'm pissed, and now I'm doubting my decision to not get her tested until at least 2 years of age.  My plan was to wait until 2 years, and then ask about it again, unless she showed signs.  Now I'm confused and upset, and I FEEL like a bad mom, that's the worst part!