How can I train my little Abysinnian Guinea - pig to be more friendly?

I have a little approx 1 and a half yr old guinea pig and she is very shy she comes out to eat some lettuce or food but as soon as she sees somebody she runs back into the covered sleeping area where she cannot be seen. Also when I hold her she's always trying to get away and nibbling on my finger, sometimes ill spend about half an hr with her and only at that 25 or 30 minute mark will she start to settle and become a bit more calmer. Im just wondering if there is a quick way to settler her a bit more. She also lives with my brothers bunny who she gets along fine with.