Is this mold?!?

So, my makeup brush broke and I look inside and at the bottom to can see some white stuff and I thought it was mold and I asked my sister and she said it’s just glue but I said why would there be glue at the bottom of it? So I decided to ask you guys so it would be great if someone who actually knows if it’s mold tell the truth💀😭💀💩💩🤮🤢🤮