she hasnt changed she still worries about her family
Metonymy is the answer. METONYMY
According to the internet, the Friar is referring to Juliet's parent that them crying is normal and natural, but since Juliet is in a better place, they should rejoice for the dead and that her soul is still pure when she goes up to heaven because she is young.
Or,
Natures tear meaning natural tears, merriment meaning happy. It is natural to cry over the death of a child but they should be happy she is going to be in a better place.
The sentence "Moreover, it is probably just as valuable or more valuable to us now, than it was in the ancient past".