As someone who changes her bed linen at least once a week, I would most certainly not expect my host to change the bed linen for me, twice, for a total 3 night stay.
If it's that important to me I'll bring my own linen.
No, if it was my guest I would not change the linen, unless someone else was using the bed in the interim, then I'd wash it. It's easier to store clean linen.. I would cover it with a spread to keep it fresh.
I don't know if it's MOST. In some communities it's considered acceptable, but in many it's not done. MAYBE MAYBE for a 3 day YT, but not for 2.
So we can't jump to assume OP and her guest showered.
Nor can we jump to the conclusion that everyone showers every day even when its isn't yom tov.
We're talking about sheets that were used for 2 nights, a person who almost certainly showered before the chag, and may (or may not) have showered during the chag. One day without a shower. I can't imagine sheets being dirty under those circumstances.
I say wash them if you want, but its fine not to wash them.
Not only wouldn't I wash it, I wouldn't even remake the bed to make it look fresh. It's "their room" for the time being and I wouldn't even walk into it, just like I wouldn't during their actual stay.
ETA: about the "most" people showering on YT.. I wonder if "most people" are aware of all the halachos? I went through the list of requirements for YT showering with DH and really wonder if everyone is doing it right. Just as an aside.