Really there's no good, non-tacky way to do that.
About the best she can hope for is if someone asks you, her mother or another close person what she needs, you can say "Well, she needs a toaster, a coffeemaker, a set of queen size sheets, her bathroom is blue and she needs towels" and so forth...then it is you who are doing the suggesting and not she who is doing the asking.
Generally, housewarming gifts (at least in my neck of the woods) are thinks like candles, plants, wine, maybe some cute little cocktail napkins or a little gift basket with the makings for a spaghetti dinner or something....and that's if the person is really close to the new homeowner.