Sorry for the first post not reflecting a warm welcome. I will give it a shot.
First, lacrosse can be a wonderful sport for your daughter. It rewards, fitness, resilience, skill development, and teamwork. I was very fortunate that both daughters chose it over soccer (no offense to soccer folks), and have generally enjoyed the experience the past 10 years.
You have good access to lacrosse development in your area. Not an expert on rec leagues on the Maryland side, but you have two good youth clubs in Bethesda Lacrosse Club and M&D DC.
Tryouts are generally in July and I believe both clubs would have A and B level teams at the 6th grade level, so no pressure if your daughter hasn't had enough practice to make the top team.
There are also lots of high school girls in the area who have business working with youger players for technique practice. And I'm sure that your daughter will have friends at Middle School who play and could organize some workouts.
I don't believe that CJMS will have interscholastic lacrosse, but Churchill plays in the Maryland 4A division and will have a competitive schedule.