My mother have been loosing weight the last year, she is down to 46 kg now. they did scan's, blood work and colonoscopy, found nothing wrong, she eats healthy but is still loosing weight. she is not ill, just complains about her bones hurting.

Keep investigating.: Investigation into cause needs to continue here. Her weight loss sounds significant, and she does have symptoms which could be targeted for testing. Unintentional weight loss could be a harbinger of a significant underlying issue which needs to be elucidated. Her bone pain may be the hint that we need to solidify a diagnosis.