I don't know about triplets but I do have twin girls who just turned 2. I have a raised ranch so I have to go up and down stairs just to get in my house. Stairs were VERY hard later in pregnancy. Plus I was on bedrest starting at week 25. That is a very real possibility for your daughter since she has triplets.
While I agree that upstairs bedrooms may be nice later on, she should really consider staying on one floor for a while. Maybe turn an office or the living room into a temporary bedroom? She will not want to carry little babies up and down the stairs all day. Think about it: How many trips would that take?? A LOT!! Plus, if she has a c-section (like I did), that makes recover harder and longer. Stairs will probably not be her friend.
I would strongly recommend that she try to set up the house so that all her essentials are handy for the first few weeks -- bathroom, bedroom/sleeping area, laundry, kitchen (or make-shift kitchen). Also, after I had my 3 c-sections, I couldn't lay flat for a while b/c I couldn't get back up due to the incision. I slept in my recliner for at least 2 weeks. Something to think about.
I wish her the best of luck. How exciting!!!