Gaffiot says it means "nurse" Lewis & Short says it means "a female waiter"
The short of it is that we don't know for sure. There are actually two issues with this word. One, it's a hapax legomenon, which means it only occurs once in all of Latin literature, and that is in Plautus' Miles Gloriosus. Plautus uses an archaic Latin, and not every word he uses was used again in later literature, leading scholars to merely conjecture what the word might have meant.
There's an even more serious issue, though: the word might not exist at all! The reading of toraria there is uncertain, and has been replaced in other editions with ceraria ("the woman who supplies wax candles for sacrifice") or gerula ("the nursemaid that carries the children").1 Leo's edition, for example, which is found on the PHI website, uses ceraria instead.
Interestingly, the Oxford Latin Dictionary doesn't cite this passage for any of these words, and it altogether lacks an entry for toraria.
Assuming the word toraria did exist, it's still not clear what it must have meant, though some have speculated. Riley, for example, must be connecting it to torus (literally a cushion for a bed, but transformed by synecdoche into an actual bed or couch) when he says the word means "mattress-maker."
Torus however can also mean "a muscle, considered as a protuberance on the body" (OLD). The waiter/attendant part comes in from assuming that torus in the is equivalent to the Greek ὠλένη, and so a toraria is "one who waits at the elbow", i.e. an attendant. This isn't waiter in the modern sense of someone who serves you food, but in the older sense as a type of servant, many of whom just so happen also serve food at dinner (and thus calling modern severs waiters/waitresses is to evoke the old servant language, but I digress).
Similarly, by "nurse" Gaffiot doesn't mean "a doctor's attendant", but in the older sense of dry-nurse, "one who protects or that which nurtures, trains, or cherishes" (Etymonline), which formed from the idea of a (wet-) nurse, who suckles infants. So both "nurse" and "waiter" here essentially mean a female companion.
What the word really means though, if it even really exists, will remain uncertain unless additional examples of its use are discovered.
1. I don't have a critical edition on me, so I'm getting this information from Riley's translation.