There are millions of plus-sized women in the U.S., but finding fashionable clothes in their size can be a challenge.

It's one Nadia Boujarwah knows all too well.

"I've been a plus size woman all my life. And some of the most formative memories for me were on the shopping floor and how painful it really is to shop above a certain size," Boujarwah, Dia&Co's CEO and co-founder told CNBC's "On the Money" in a recent interview.

Nearly 70 percent of American women are size 14 or larger, according to market research firm Plunkett Research. And yet, only 18 percent of the clothing sold in 2016 was considered plus-size, market research firm NPD found in a recent study.

Since the retail industry isn't catering to this majority, Boujarwah said, the average plus-sized woman "is only spending 20 cents on the dollar that women in smaller sizes are spending on apparel."

In 2014, Boujarwah left her investment banking career behind to launch Dia&Co, a style service company dedicated to women size 14 and up, with her co-founder Lydia Gilbert. A spokesperson for the company said the styling service has had more than 1 million users and ships to all 50 states.

"Eventually I realized I wasn't alone, there are 100 million women in this category, and really being a part of creating change for such an incredible community of women was enough to leave the Wall Street job," the entrepreneur said.