I have two LEGAL versions of minecraft. How do I play with my kid?

My 5 year old is really into minecraft and wants to play. If I create a server she can connect to it and play, but if she creates a server I can't connect to it. It must be my firewall? I bought TWO copies of minecraft. Her cities are much nicer than mine so it'd be more fun to play on her server.

Here's how we connect.

1. I start a single player game and "open to lan" it gives me a number.
2. I go to IPCONFIG in CMD and find my ip.
3. She writes it in if it's not there (after the first time, it always is unless she accidentally erases it)
after the I{ and the ":" she enters the number and connects to my minecraft.
4. Unfortunately, I can't connect to her minecraft even though our computers are virtually identical and on the same network side by side. Neither of us can connect to the servers outside, if there are any.

I realize this isn't elegant but it works in one way. For owning two games that cost around $50 together it's frustrating.

BQ
She sometimes gets disconnected from me. What's up with that?

Added (1). I'm using Windows 7 firewall and have even tried to turn it off to no avail. I haven't yet done any changes to the router because I don't know what ports minecraft uses.

Na, man, you need to use a better Server. That's where your problem lies, most likely.

I have a small server you two can play on and ill create a separate world for you. 69.10.58.115:25564 it will take a few hours before i can and ill let you know when its up