Welcome!What Hardware version is your router? Look at sticker under router.
What
Firmware version is currently loaded? Found on routers web page under status.
What region are you located?
Some things to try:
Might set up a QoS rule for her LT and one for your PC. Set hers for a low priority and yours for a high priority.
Turn off Advanced DNS Services if you have this option under Setup/Internet/Manual.
Turn on DNS Relay under Setup/Networking.
Setup DHCP reserved IP addresses for all devices ON the router. Setup/Networking
Ensure devices are set to auto obtain an IP address.
Set Firewall settings to Endpoint Independent for TCP and UDP under Advanced/Firewall.
Enable uPnP and Multi-cast Streaming under Advanced/Networking.
Wireless Installation ConsiderationsWhat wireless modes are you using? Under Setup/Wireless/Manual.
Try single mode G or N or mixed G and N on the host router?
Channel Width set for Auto 20/40Mhz or try 20Mhz only.
Try setting a manual channel to a open or unused channel.
What security mode are you using? Preferred security is WPA-Personal. WPA2/AES Only. Some WiFi adapters don't support AES, so you might want to try TPIK only or Auto.
Any cordless house phones?
Any other WiFi routers in the area? Use InSSIDer to find out.Turn off WISH, and WPS under Advanced.
Turn off Short GI, WLAN Partition,and Extra Wireless Protection if you have it. Under Advanced/Advanced Wireless.