Why did they say "Tagidi" (singular)? Above (verse 14), they said "Tagidu"!
Radak (14): Above, they did not suspect her of telling that they were in her house. She covered up for them to the king's messengers! They stipulated about her family. Here, people will realize why she gathers her father's family to her house. They forbade her to tell others with a house in the wall about the Siman, lest they do similarly.