Frankly, the Fun or 2Fun are the logical recommendations for something more aggressive than the Little Hero for you. An EZG 50 might another option. IMO the best alternative to the Little Hero for you would be the new Deisel 60, which is a super great boat, too. Of course, there is no shortage of boats to chose from. So, it won't all be about the boat. One thing I preach to women kayakers is to boat early, boat often, keep it fun, don't try to advance too quickly, and maximize your aggressiveness as you advance in class ratings (meaning attack the river, slicing and dicing it, learning skills and control before you advance to faster, steeper, more powerful, more technical runs). It does seem you already love and will continue kayaking. So best wishes for having fun.
No risk, no reward. It is not that we have to, it is that we get to. Preparation and education are essential to self-confidence and success. - KV
"If there is no risk there is no adventure."- Bill Briggs