First think, and be honest, is your dancing extraordinary? Do you think later in life you'll be happy with the decision of choosing dancing if in case you're struggling? When you see people around you making more money than you, earning more respect (Because to be honest, no one will respect a dancer until they've achieved a big name for themselves. Otherwise you're just another struggling wannabe), will you be able to stay motivated and free of insecurities?
Unless the answer to these questions is a definite yes, then only it’s suggested to go for dancing as a career. And if the answer is a definite YES, then there is no point looking back, she is your mother, convince her, she will understand