Swig hasn’t been paying my gf.

My gf works at Swig and was told she would be getting 10 dollars an hour PLUS tips. Repeatedly, her paychecks are significantly smaller than expected when we do the calculations with tax accounted for and we double check ADP and her manager had a really confusing reply saying “We get paid Bi-Monthly not Bi-Weekly.” It sounds like bull to me because I’ve never heard this kind of thing. Are we crazy, or is this a thing? If so, what should we do? It’s been about 6 weeks of working there and still no proper payment.