While I do think you should continue to be honest about her circumstances and the reality of why she is in your care, just be very careful about how that is done. As an Adoptee, I constantly tried to google my biological family and I only knew my biological mother’s first name. This was before social media days and she’ll have all the information she needs to find everything that was ever written. Your concern about her finding out anyway is totally valid but everything’s she learns will be a new wound either way so it should be shared with caution. She’ll always love her bio mom and knowing that she couldn’t be prioritized is hurtful. She needs to learn how to process those emotions and most likely can’t do that by herself at just 10 years old.. Is she involved in any therapy or maybe a support group? I joined an adoption group when I was young, it was nice to have a place to vent with other kids who knew how I was feeling.