It sounds like your routing is the issue here! as long as her router is doing the NATing AND you have the correct routes inplace then there should be no problems.
Get the IP address of the servers you want to connect to, then get your moms routers IP (local) and in windows (im assuming your using) through cmd create a static / persistant route to the destinations you want to get to and just add her router IP as the gateway and you should be good to go!