This is the 517th most frequent Russian word.
вся
"Вся" means "the whole" or "all" (feminine form).
In this sentence, "вся" is used to describe the entirety of the room (room = "комната"). It emphasizes that the entire space mentioned was adorned with flowers.
Вся комната была в цветах.
The whole room was filled with flowers.
Here, "всей" (a form of "вся", in instrumental case) refers to her entire soul (soul = "душа"), showcasing utmost dedication.
Она сделала это со всей душой.
She did it with all her heart.
In this example, "всем" (a derivation from "вся", agreed with "все", in dative case) refers to every person involved, indicating inclusivity.