Odd that someone would be civil and say nothing, then call the park police. It could happen, she could change her mind, the two could get together at the trailhead and feed on each other for attitudes. Highly unlikely.
A park, how far and for how long might someone hike. Are the authorities so bored that they can go sit in a parking lot for hours, or might you camp? Would the women press charges? In court, a witness is needed, in this case two witnesses to prove it, and who wants to pursue such a thing after experiencing a nude hiker as harmless?
I like to act as if nothing is not ordinary. With conversation, I might sometimes say, "hope that you don't mind nudity?" The message is that I'm not here nude for you, I'm here to enjoy the day and was surprised to see someone. Perhaps, "Oh, I didn't expect to see someone else."
It depends where you are and how many. I don't regularly hike in places, except more traditional nude areas with a history, or expectation. One complaint is harmless, two or more complaints and suspicion may be aroused.
Jbee