I don't think any woman would regret having children unless she was too busy trying to become a man, then there is no time for being a mother.

Or, if the woman married for money, had children, and not out of love, then there can be some regret, but not to the extent of the first example.

Or, if the woman had children out of love for a man and for his children, or for just the love of children, and after the man did not take responsibility to provide anything, then this is cause for some regret, but not as much as either above examples and not regret for having children, but regret for who they had them with.

Finally she might regret it if something was wrong physically or mentally with the child but only for the sake of the child's quality of life and feeling guilty more than regretful, a mother wants the best for her children that's all.