How about I send my boss a text without telling my mom when she told me not to.
Oh no, you can't be serious. Don't you think she will find out?
She won't check my phone history when I'm lying
You shouldn't do something your mom forbids. Have a conversation with your mom about why she doesn't want you to text your boss. It might help you listen to her if you understand where she's coming from.
She thinks I'm too young for a phone, it's not fair.
Well, for now just listen to your mom. Your boss is your boss though and if you can work you can get a phone. It depends on what the text says, which I don't know about.