"Waiting for chunk..." or "Loading terrain..." when joining a LAN game
It sounds like your friend just has utterly garbage upload connection—a lot of residential connections, especially DSL, are much faster downloading than uploading, so your friend might be able to download the Minecraft data from your server just fine, but be overwhelmed uploading the same amount of Minecraft data.
You can work around this by having your friend reduce the render distance in server.properties so that she has less to upload.