Baking soda mixed with a solid oil like coconut or shea butter. Their hair will still be a terrifying lost cause if they won't wash that in the sink, but with enough deodorant you can get by the rest of the way. People do it for hiking or dealing with complicated casts. If its not serious, she'll get uncomfortable and start showering, if it is that serious a phobia, it'll help to have something of a halfway point between like never showering and normal hygiene.

help her put together the emergency shower kit it has a robe pullover t-shirt flip flops or Crocs she's already got a towel and pair of shorts.

Get her moved due to hygienic reasons you can't live with someone like that it's unsanitary.

I had that happen in college. Standing on the sidewalk with one shaved leg in a shitty cheap robe for an hour was not fun. Maybe offer to get your roomie a nice robe and shower sandals so if it ever does happen, she'll be ok? If it's danger she's worried about, maybe have a sit down with the RA or campus emergency services to help sooth her fears. or get her some of those cleansing body wipe things.

Just have some of your friends gang up on her with you and throw her in the shower and make her scrub herself until she is clean and threaten her with the same treatment everyday if she doesn't follow through.

I suggest she go to an on campus health counselor or nurse.

Maybe she shared this with you because she wants your help and support. She obviously trusts you enough to tell you this. If you can't help her than maybe you can find someone who can. Sure, it sucks for you because she probably smells, but it can't be pleasant for her either because she's probably embarrassed that this causes her so much fear and anxiety.

Um, no you don’t. Switch roommates or help her get over her fear because that’s unrealistic to maintain