As an introduction, let me say that the best possible approach for market sizing is the one that maximizes Simplicity * correctness i.e. gives you a feasible range for the answer and directs you towards the correct action / solution for the client using less data, assumptions...

That said, to be more precise you could further segment the crime rate on the basis of the size of the cities, e.g. metropolitan cities vs. medium cities, vs. small villages and change accordingly your "conversion rate" for the women that actually face these crimes (e.g. metropolitan cities 50% more vs. small village)

You used a "demand side" approach to the market sizing, which to me, seems pretty good choice, but you could have used a supply side approach

E.g. (high level), you could estimate the number of crimes in each type of cities based on drivers. You could start from the population of each type of cities, segment by age and assign the probability to be a criminal (crimes / population) and then assign a % of this crime to be a crime against women.

You can further sopistichate this approach, too