Picking up dachshunds

How do you politely correct people when they pick up your dachshund/hold incorrectly. I always tell people when they meet her, "If you hold her or pick her up make sure your always supporting her but and chest at the same time she is prone to back problems". But people keep holding her by her armpits and extending out their arms to look at her . I'm very non confrontational and I just freeze because i don't know how to kindly correct them. I know it's bad for her and I need to speak up I just can't find the right words.