How old is she? My daughter is 11 and over the last year she has become a lot more willing to have a bath/shower (always used to go through a battle before).
Work ethic, if you're referring to school work, is she at comprehensive school yet?
My daughter is very direct and confident with her friends (embarrassingly so), but in school they don't hear a word out of her. She is in all the top sets and says she is happy to listen to others and make her mind up from there. She has always been like this, it was bought up at primary school. Her closest friend is the same and incrediably bright. It's not necessarily a bad thing to be quiet, I got my last job because the other two candidates were so full of themselves at the interview. turns out they wanted someone quiet who would fit in with rest of the staff.
I guess you've tried it, but would she respond to you sitting down nicely and covering one subject at a time, ie hygiene, mention that all her friends will be bathing or washing everyday. and she doesn't want to risk smelling and or having noticeably dirty hair as other people don't like that.
Where things need to be addressed, then you have to deal with them. Like you say you don't want to knock her confidence, so tell her she looks nice, her hair looks lovely and shiny after she's just washed it, compliment her on anything positive or helpful, or on homework she's done. I'm sure you do things just with her, but perhaps have a few hours in town with just her - if you go into Boots, she may like to choose a few toiletries herself (might encourage her to use some of them!).