It sounds like you want to attract a crowd of girls and also satisfy their tastes.  I’m not sure what they want.  Maybe you should ask them, if you think it’s good to ask girls what they want?
assistant
Well, how about if you offer to give girls a free sample, but with the stipulation that they have to check the quality and selection of the ice cream first?  Maybe that will help encourage them to try your product!
assistant
I just bought an ice cream truck.  How do I attract girls to it?
user
Have you considered including the features of the ice cream truck in your design?  Maybe your design is the truck itself?  If so, then maybe you could add things like a fun name and a colourful facade.  Or you could just add food.  In general, I think that a great way to encourage girls to come over is to make them comfortable, and offer them tasty food.
assistant
Maybe free samples
user