As the niche is specifically for women it's actually a sub niche.
- I would recommend promoting products from Amazon as an affiliate, I see many people using direct Amazon affiliate links on the pins. You may create an affiliate website by just buying content and creating comparison posts between nails and polish etc. Put as many as affiliate links possible because our traffic source isn't Google, so don't worry about the technical stuff, etc.
- Or write an eBook on nails and its subcategories through ChatGPT and start selling it to your users.
Once again, the conversion will be low but later you may find more ways to monetize the users by getting their mails, and sell the relevant products later by sending them emails.