Factors associated with chronic exposure to warning-sign behaviour (WSB) in girls' romantic relationships need to be understood in order to develop responsive prevention programs. Data was provided by 152 Australian adolescent girls (M = 14.7 years, range = 13 to 17), 66 of whom reported recent relationship experience and exposure to at least one WSB. Guided by the dyadic slippery-slope model of chronic partner abuse, relationships were tested between frequency of WSB exposure, perceived WSB risk, confidence in self-agency, and assertive tendency in romantic relationships. Girls who reported more assertive responses to WSBs reported less frequent exposure to WSBs in the past 3 months. Risk sensitivity, while weakly related to assertiveness in non-WSB-exposed girls, was unrelated to assertive tendency in WSB-exposed girls. Girls with greater WSB exposure had lower perceived self-agency, and lower perceived self-agency was associated with less assertiveness in response to Dominance and Possessiveness WSBs. These results are discussed in relation to dyadic slippery-slope theory, and point to the potential importance of strategically timed, empowerment-oriented programming in partner abuse prevention.