Answer: b. She used to wear pretty clothes and be lively-when she was Minnie Foster, one of the town girls, singing in the choir.
Explanation: In this sentence (and several other remarks) we learn something that is, plot-wise, very important about Mrs. Wright's past: she used to have a liveliness in her youth (before marrying) that is now gone and at some point in the last 20 years, she has stopped wearing pretty clothes.
I'm assuming that if she had a pretty box, Mrs. Hale said that based on the fact that She used to wear pretty clothes and be lively - when she was Minnie Foster, one of the town girls, singing in the choir.
Treasure in the first usage means precious gems like gold or silver . In its second use, it means to value something. Hope this helps. We could help more if I had the poem for sure posted here but this is the meaning from the poem I think you are talking about. Have a great day!