[Uncle Peter]

I think that 20-30%ish CPU usage is normal tbh. Just wondering if you're running a direct connection or via relay? If you're not behind a firewall/proxy then you should be using a direct connection to obtain the best call quality:

In options, check the "connection" page. The "Use port 80 and 443 as an alternative for incoming connections" should be unchecked on both your own and your girlfriend's machines.

You will of course need to ensure that the port specified in the "Use port XXXXX" for incoming connections is forwarded to your respective machines if you are using a router.

Another thing you can do is go to the "Advanced" page in options and check the "Display technical info" box. This will display the call quality, packet loss and various other useful stats when you hover the mouse pointer over the person's avatar/icon when in a call. This might give you some clues as to whether or not your network connection is causing quality issues.

hth