a tough cookie
A strong, determined person who is not easily intimidated, discouraged, or defeated. Our principal was a little lady, but she was one tough cookie! She had a difficult childhood, but she's a tough cookie. I know she'll be a success.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a tough cookieor
one tough cookie
If someone is a tough cookie or one tough cookie, they are confident, brave and determined. A pushover is not how I'd describe her. Behind that sweet smile, there lies a tough cookie. He has a reputation as one tough cookie.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
a tough ˈcustomer/ˈcookie(informal) a person who knows what they want and is not easily influenced by other people: Self-confident, ambitious and positive, Paula is a tough cookie who is bound to do well.
Farlex Partner Idioms Dictionary © Farlex 2017