In terms of structure, the example started with a title, introduction, then sections with headings and key points as bullet points. Maybe follow a similar format for consistency.

Researching the key points for 2021: During 2021, many countries were in the early stages of pandemic recovery. Teenagers had just started returning to in-person education, social interactions changed due to remote learning, and social media usage increased. Movements like #MeToo and climate activism were still relevant.

Possible challenges: Determining the exact relevance of certain trends to 2021. For example, sustainability in fashion was a growing trend, but how prominent was it specifically in 2021 for teen girls? Also, verifying dates for social media trends and ensuring that the data is up-to-date as of 2021.

I should also think about the audience. If it's for a general audience, the content should be accessible and cover broad topics. If it's for an academic or professional audience, more data and specific insights might be needed. However, since it's about teen girls and 2021, probably the general approach is safer.

Need to make sure information is accurate to 2021 and not mixing with later years. For instance, the Delta variant was a big issue in 2021, affecting school reopenings and outdoor activities.