"My people, you who are like a daughter to me" or "My dear people". Jeremiah shows Yahweh's love for his people by speaking to them as a daughter. See a similar phrase in Jeremiah 4:11.
"put on the clothes that show you are mourning" or "prepare to mourn". The command "gird yourselves," which usually means "prepare for work" or "prepare for battle" is ironic: they are to prepare to mourn, not to work or fight. See Jeremiah 4:8.