Hi Jose, I figured I'd chime in w/another girl's perspective. I can totally relate to your friend's experience, as I've been there. I've been riding now for 15+ years (all of them w/my husband...and we are still together;). While providing feedback to her is very important, you also need to just let her ride, and feel everything for herself. Give her a chance to absorb any info you've previously provided and finding a comfort level for herself. But, let her ride, and feel it. Offer to take out the video camera. With video you can show her what she "is" doing, and then explain what she "should" be doing. This is a very good tool for anyone that learns better with a visual.
Going faster=FEAR for some (not everyone is an adrenaline junky!). Each person is different for how they will handle this equation. The more comfortable she gets w/just riding, the easier it will be for her to start riding faster. Hope this makes sense.