@Derpyfan  
Trixie: “I sleep in a hammock in my wagon do you?”  
Starlight: “I sleep in a single bed in my own room an the Princess’ Castle.”  
Trixie: “…oh ya…”

@Otterhand  
She also lives in a wagon.

Well Trixie sleeps in a hammock.

@Background Pony #564E
 
@DTavs.exe
 
Pinkie pie her bed is so large so her sister can sleep with her whenever she visits rarity is a bit of a drama queen so she demands the highest comfort and space for a bed Twilight on the other hand she has a bed that’s larger than what she needs I think it just came with the castle fluttershy’s bed is big because I assume some of her animal friends don’t like to sleep alone so the extra space is so they can sleep with her on the bed and considering how rainbow – sleeps if she tosses and turns and rolls all night while she’s sleeping then it would make sense for her to have a larger bed so she doesn’t fall off it
 
An Apple jacks bed is I assume just in case it Apple Bloom has a nightmare and she doesn’t want to sleep alone

@Background Pony #564E  
Holy crap you are right, I hadn’t noticed that.

@Background Pony #0D1E  
The mane six all sleep in bigger beds with room for two ponies.
 
Fluttershy: >>404090  
Rainbow Dash: >>1582121  
Pinkie Pie: >>1868434  
Twilight: >>1954271  
Rarity: >>1172240  
Applejack: >>1225637

Well, she is not married, it make sense she sleeps on a single bed, why you think it is unusual?

why is that unusual?