I've been wanting to ride to work, so I can relate to that problem. Aside from packing a change of clothes, I'm not sure what to recommend. Leaving early (before the weather gets hot) might help.
My hope is that if I get used to longer and longer rides, the distance to work won't seem like that much exercise and I won't arrive out of breath and sweaty. Guess it all depends on how far you live from the destination and how hard the terrain is. Good luck to her!