I have a skype phone number. My daughter is in France, she dials that number on skype and the call if forwarded to my regular phone. The calls aren’t free but they are really cheap. I notice that if I’m near my computer I hear a crackling noise like cellophane being crumpled. She doesn’t hear that noise. You might want to check for interference, maybe something electrical is too close to your computer.
OK well if she signs up for google voice using her skype number, it is possible that when she initiates the call to the US that she can save even MORE if she does so using google voice.
Of course, you know that if she skype calls your computer, then neither of you pay anything, right? And if both of you have videocams embedded in your computer, then this can make for a videoCall...you have done this?