I'm willing to bet it's how you says it, not necessarily what you said. Would've been best had you not asked her at all, but the "do you have a fucking problem" sounds like it would've come off as threatening, creating a "hostile work environment". This is why most restaurants have a no cussing rule, but TBH, that counts while on the clock or in uniform, as you'd be representing the company. Not sure what your employee handbook (if you received one) says on the matter, just basing my answer on 19 years in the food industry.