Solution: No need to apologize, since that would imply that you, or the kids, did something wrong.
"This isn't so much about gender as it is about creativity and development," said Anthony Rao, Boston-based psychologist and author of "The Way of Boys: Raising Healthy Boys in a Challenging and Complex World."
"One of the big goals in this age range is learning how to take on different roles and take other people's perspectives and start to understand that the world is full of people who do all sorts of jobs and have all sorts of personalities.
"A lot of these lessons are learned through play, often by putting on different costumes. This is completely developmentally normal," he said.
Nonetheless, a boy dressing like a princess touches a nerve for some parents.
"I tell parents, 'Let's take all of our preconceptions and all of our baggage and feelings about gender, and just take it off our kids,'" Rao said.
"They're at an age when they have a lot of normal curiosity and it doesn't predict anything about the future. It's really just about play."
If this particular boy decides, down the road, to dress in women's clothing, it won't be because the neighbor mom let him at age 6. It will be because he wants to.
"Parents certainly have so much power and influence over who their children become," Rao said. "But they're going to separate from you, and they're going to be themselves. And if parents can accept that, and let go of the fear and anxiety about sending their child down a certain path, the relationship will be much better for everyone."
As for the relationship with your neighbor, well. "I think you could sort of use some modeling here," Rao said.
He suggests saying, "We just see this as one of the many things girls and boys do, and if you or your son is uncomfortable, let us know, and he can opt out. We'd certainly like to still be friends."
"No laws were broken, no harm was done. I think you approach it as, 'We're a big, happy neighborhood and we all make our own choices.' And then you let it go," he said.
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