Women's dressing

Q: I live in Saudi Arabia, and I just got engaged to my cousin who lives in USA. I'm aware of the cultural differences between the two countries. I'm worried about how my cousin should wear clothes. I didn't ask her to wear abaya because she said that girls in USA don't have to wear abaya and it's not necessary in order not to get men's attention, like in Saudi.

She also works in big well known company in an office environment with men and women together. I would like to know what Islam says about wearing jeans (not tight), makeup (little bit) and high heels shoes? And is it ok to work with men in an office environment, and is it ok to ride in a car with a male colleague?

2. How should Muslim men and women conduct with their brothers/sisters in law? Is it ok to talk or sit together with them in a family gathering? Is it ok to travel with them together with one's husband?

3. Is it ok to shake the hand of a non-mahram?