Breaking down barriers is tough. Many companies make the mistake of dismissing diversity early on, only to realize later how foundational it is to their success or failure.
Once your company grows past a certain point, upholding values becomes more and more difficult. This is where companies get into trouble. Thus, it's absolutely critical to take your company values seriously and practice it every day.
Be transparent about why the termination is happening. If you did things right, it shouldn't be a surprise to the person.
Values are the foundation of a company. Culture is the manifestation of values - the day to day actions and behavior. Adapt tactical cultural behavior that helps you execute on your values.
People will never stop having kids, and people will never stop spending money on them to make sure they're safe, healthy, and educated.
While your intentions may be good, this is something every expectant working mom fears - being phased out. I'll put myself out there and admit this has been/is a fear of mine. Let her be the one to decide whether something's too much for her to handle or not.