Quantasia Sharpton declaring "I need money" has nothing to do with her lawsuit against Usher -- she's just struggling financially like millions of Americans ... according to her lawyer.

Celebrity attorney Lisa Bloom tells TMZ her client has been raked over the coals since her Monday morning news conference. In particular, Bloom defended Quantasia's social media post saying she's hard up for cash ... which came one week prior to the suit.

Bloom says it's unfair to connect the two things -- "It's not a crime to be poor in America. It's not a crime to be honest about the fact you need money. Most people need money." She points out Quantasia didn't put a dollar amount on the lawsuit, and only wants what a jury deems fair.

In addition, Bloom says Quantasia's been repeatedly fat shamed online since the news conference.

As for the tweet about her last hours as "a regular girl" -- just before going public -- Bloom says it's only natural her client was nervous, but still ... she's been "so brave to step forward."