1. Dear Graham, can you please clarify one issue. Whose visa application is the question about - your wife or her daughter? Are you asking about extending your wife's visa or getting a visa for her daughter?
2. Dear Graham, the daughter of your wife can get a visa to live and work in the UK as the "dependent" of you. However, you will need to show some evidence of dependency. The fact her daughter is 16 (under 18) is evidence of dependency. However, some element of financial support will assist your application. Here is a link to the UK Government website which sets out how to apply https://www.gov.uk/remain-in-uk-family/overview
3. The application can be made from within the UK. There is no need for her to fly back to Brazil. Here is a link to the application form and guidance on how to fill it in. https://www.gov.uk/government/publications/application-to-extend-stay-in-the-uk-form-flrfp
4. Dear Graham, see No. 3. The name of the form is FLR(FP)
5. You are welcome. Please Rate the answer.
6. I know the form seems inappropriate for a child joining their parents. However, this is the form the guidance states that you fill in. If you read the UK Government website I indicated through from "Apply to remain with family in the UK" this is the form they make all other applicants other than a partner fill in.
7. Could you please Rate the answer as unless you Rate the answer your expert does not get paid for answering your question. There is no point in saying "thanks"