I could tell that she was at St. Joseph's by looking at the image of the census. She's listed as an orphan, and the adults in the same household are listed as being in St. Joseph's Convent.
My grandfather's birth month and year is listed incorrectly on his headstone, so I always take dates (and spellings of names) with a grain of salt. My husband's great-grandfather's headstone has the wrong middle initial. And when my aunt passed away last year, her kids listed her mother's name wrong in her obituary.
The information is only as good as the person giving it. It's possible the person supplying the information to the census worker wasn't sure of her age.