OH MY GOD ... You people are giving her the wrong information!!!!!
Medical exam IS REQUIRED for extension of family visit visa. (this is what I did for my family)

The requirement states:

If the visitor wants to stay more than one month inside the country, he/ she has to undergo a medical test before the month ends. The visa is renewable for five months for immediate family (father, mother, sister, sons) and two months for other relations.

Get the official requirement here from Hukoomi website:
1. Go to Hukoomi. (you can google it)
2. Go to How do I?
3. Select get residence visa for family
4. On the next page, click on "for more information, click here"
5. On list of services, click on "Visas for Family Visits"

Hope this helps and do your medical (at the Medical Commission) soonest. Don't forget to do the blood grouping first.