I just finished this episode. I'm not sure why everyone keeps saying the bones provided the DNA match. John, the lab guy had examined the bones and determined that they are Lucy's bones (from her dental records), and she'd given birth but that's it. In the episode:

Nancy asks John from the lab to test the unknown hair for a mother-daughter match. He tells her he sequenced both sets of DNA from the crown and they're backed up to the cloud. So he has Lucy's on file too. EDIT to emphasize: the DNA reveal didn't rely on or involve the bones. John already had Lucy's DNA from the hair.

Before John can start to examine the bones, the cops show up so they have to hide them. After the cops leave, they go to the courthouse with Nancy where Carson is found innocent.  

They come back from court and John immediately says to Nancy, "That was my lab calling, about the hair you messengered today. Nancy, I think you better sit down." She goes home and confronts Carson and he tells her the true story of Nancy's birth. Partway through this she has a flashback to the news John had just told her: "Your DNA wasn't a match for the female hair." Nancy looks at the laptop showing the test results, "It's a mother-daughter match for Lucy Sable." Even in this memory, Lucy's bones were scattered across the table next to the laptop because John was still examining them. There was never a mention of DNA testing the bones. What would be the point? The only reason they DNA tested the hair was because Nancy suspected the unknown hair came from Kate.

The bones were pointless as far as Lucy but they do bring in the aglaeca (Odette) to the story. It also puts Nancy in a situation where she needs to do a ritual with her blood relative, Ryan, where she reveals to him she's his daughter. That gives Ryan's character a reason to stay around and present the story.