How does Emilias description of a jealous person fit Othello?

I think you are referring to this quote,

EMILIA

But jealous souls will not be answer'd so;

They are not ever jealous for the cause,

But jealous for they are jealous: 'tis a monster

Begot upon itself, born on itself.

Emilia says that alpha-men like Othello don't need a reason to be jealous. Othello's jealousy and paranoia feeds on itself. Othello only needs a seed of doubt to germinate in his head before it becomes a full blown obsession.