Since a few days ago, it stopped working. She even tried using my IP address directly in her browser, but that too, didn't work.
Then I remembered, Windows 10 updated something a while back, and I guess it was then when this issue started. Turned out, I had to allow port 80 over my Windows Firewall again. So, if you're running Windows 10, here's how to do that:
Press the Start button, and type in Firewall, then click on Windows Firewall with Advanced Security at the top:
This will open up the Firewall window, which looks like this:
(click on the image to see it bigger if you need to)
What we want to do is set up a new Inbound Rule, so at the top left, click on Inbound Rules:
Then, to create the new rule, click on New Rule... on the right:
That opens up the New Rule dialogue window:
We want to open up Port 80 on the Firewall, so click on Port, and then Next > at the bottom, which will bring you here. Make sure TCP is selected, and type in 80 where it says Specific local ports:
Click Next > at the bottom again, which brings you here:
Make sure Allow the connection is selected, and click Next > once again, bringing you to this screen:
Select the appropriate settings here for your network. In most cases, the Private one should be sufficient. Finally click Next > once more, and give this Rule a name and description, and you're done with this section.
Last, but not least, restart Apache, and you should be all set to go.
Hope this helps!