How to confront new office mate regarding personal hygiene?
After some clarifications via comments above: 

There is surely an office with a name something like "Student Services" that would be the front end for many issues involving conflicts/issues between students or conflicts/issues between students and faculty. It is not possible to guess the name of the corresponding office at your university, so some experimentation or asking around is necessary. You should definitely consult with them about what actions on your part would be approved or disapproved.

There surely is an HR office at your university (assuming it's in the U.S.), which has some oversight powers/responsibilities for any paid personnel. Probably most grad students have not had any interactions with that office, but it surely exists, and does some back-end checking of hiring and such.

Many years ago, as director of graduate studies in mathematics at a U.S. "R1" university, I found myself the recipient of complaints from office-mates about the hygiene of a grad student. Having been already sensitized to the volatility of such issues, I wrote a somewhat vague, but pointed, message to all grad students in the math dept about "expectations" for hygiene, given their TA duties. Naturally, most were confused as to why I was writing this at all, but the "broadcast" aspect did avoid confrontation with individuals. Also, there was certainly the aspect that there was a job getting done for pay, and interference, accidental or not, was not ok. If the person had not been paid by our department, I would have been much more inhibited about strongly-recommending hygiene modifications, just given the way things seem to work here.