Simply seems as if City weren't interest in renewing her contract, possibly no other UK club could afford her. Steph (twice) and Karen renewed / improved deals in that time and Toni never did.
Seems from around about a year ago she wasn't needed. New strikers were coming in to replace her and the lack of contract activity didn't show she was needed. Probably become an issue in the dressing room too, manager maybe couldn't manage it.
Barcelona is a nice place to live, but the quality of football is low in Spain for women, semi pro league, find it odd she has moved out there being as I don't think she really adjusted moving to Manchester from Liverpool.
Notice that her profile has been remove straight off the women's page, yet the new striker has yet to have a profile?