Alexa's current voice recognition range is about 10-15 feet, so chances are you'll need at least two of them if you have a large home or multiple levels in your house.
Your best and most affordable bet is getting two Echo Dot speakers; they usually sell for $50 but are often discounted for $30-40 on Amazon.
With two Echo Dots, you can use the intercom feature to communicate with them or simply have easy access and the range to ask her a question. To learn more go to your Alexa app, hit the three bars next to settings, and tap the "things to try" tab.
You'll get information about voice calling, drop-in for intercoms, announcements, and pretty much everything else Alexa is capable of.