Over the age of 35 the probability of downs does increase. But, many people are able to carry children and have perfectly healthy children even after this age.
It is about where you are in life. I work with parents that find in their thirties is the ideal time to have children because of being settled in their own lives. There is more time to give to the children. Also, you have grown so much by this age, you can truly appreciate the moments that are so treasured.
What are her issues or worries with having a child at her age?
I know it is hard when the desires for family growth are split.
There are many pros, some cons being like I mentioned above and the fact that your age may become an issue while they are still young. But, if you live a healthy and fit lifestyle, you have decades of being able to keep up. Let me know some of her worries and I will try to help more specifically. I work with parents of all ages, so I understand this topic, very well.