As Troy told Annie, Britta is attracted to men that treat her badly. So to get her to lose interest in Blade, Troy sent her a “fake” text from Blade saying something really nice–something about how wonderful he thinks she is, maybe some specific things that he likes about her. The plan worked–Britta immediately lost interest in Blade.
Later, when Annie told her what they had been doing, Britta realized that it was Troy who had written these really nice things about her, and that the text may reveal Troy’s true feelings for her. A Troy & Britta mutual attraction has been touched on in past episodes.