I paid her to do it, and I've been waiting for anything to happen. I paid for every single room and so far I haven't noticed a single change. I even left the area and waited for 48 hours. Do I need to wait longer, or is there something else to trigger the changes, or what?

Any help would be appreciated Thank'ye.

i think it's a bug because it's sounds too good to be true i know that after you furnish your house you can add stuff but as for having your steward to do it yeah lol good luck

Other information in case it's useful: My house has all three wings.
Armory
Storage
Enchanter's Tower

I had already decorated a lot in all areas before I decided to look for a steward and see if they could do it for me.
I also paid for all of the other upgrades (Such as the cow, the carriage, the horse, etc.) and they all showed up instantly.

Well stewards aren't like the MC, they cannot insta-build It actually takes them a few weeks per item...

Honestly it sounds like to me that they can install the furnishings instead of you buying and building them yourself. I do not know much on the stewards yet... I'm still trying to figure out how I get a child after I've bought everything...

no it's a bug i went on the UESPwiki and it's under bugs

Never mind. My house is the one in Falkreath so I walked out and walked into Pinewatch (Just to load a different area and make sure my house wasn't loaded) waited for four more days, came back and I had everything. I waited for a week total, but it wasn't there after roughly 2.5-3 days, so you have to wait somewhere between those increments. I'd say just wait a week to be safe, and also go inside somewhere before you start waiting in case that helps.