Is it an obligation for a Muslim woman to get married and have children?

No, it is not obligatory for a Muslim woman to marry. Some women never get married although they would love to do so. Certain circumstances may prevent them from marrying.
We cannot say what a woman must or must not do about having children because this is not a matter that is decided by her. It is God the Almighty who creates. There are many married couples who have been assured by doctors that there are no medical causes to prevent them from having children yet they go through their lives childless. If this is so, how can we suggest that having children should be obligatory?