96 participants were randomly assigned to one of the two groups regardless of their motivation level. Participants in both the groups were exposed to both the experimental conditions of gain framed messages and loss framed messages. The only difference was - counterbalancing such that the participants were shown gain frame message in group 1 then its corresponding loss frame message was shown in group 2. So here the within group factor is: framing condition - gain frame and loss frame between group factor means that this should vary across two groups but in my study both participants of high and low motivation were present in both groups and exposed to both gain frame and low frame messages. Participants in two groups were different but exposed to same but counterbalanced design. I am not sure if this is a 2 x 2 mixed anova design with framing condition as within group and motivation as between group factor.
You conducted a crossover study. The proper analysis method is a bit tricky, and it will depend on what are you willing to assume about period effect (maybe the second response always tends to be lower) and carryover (maybe the effect of the first intervention lingers to affect the second answer).