As far as I've heard, from over 10 years of Tibia playing, Bubble was an ordinary player at first, who didn't receive any levels or so. Though Bubble did get lot of support from Cipsoft in various ways, and her guild frequently blocked of her favorite spawn Orc Fortress during the Dark Side vs Alliance war to let her exp freely at roughly level 130ish and higher.
Also I've heard that the player Bubble quitted Tibia years before the character stopped exping, and that the later years there were gamemaster staff members who controlled the character too use it as a "Testing character"
Proofs of tis would be that the character named "Bubble" stopped exping completely when Cipsoft renewed their screenshots with characters from a side hosted server which wasn't available too public. Before that several of the screenshots were made by players such as Arieswar, Bubble and several other very old players who've supported the server in a way or another.