Answer:
Meg overhears the Moffat sisters discussing her family's financial troubles.
Explanation:
hey are speaking about the fact that Meg has received flowers from Laurie. Because they are not engaged, the Moffat sisters discuss the idea that Meg mus be "scheming" to get him to propose. Their marriage would help correct the family's financial woes.
I do not believe a comma is necessary in this sentence at all. In fact, if you were to insert a comma after the word grazed (as you maybe tempted to do) it could change the meaning of the sentence. If you meant the lions were oblivious of the presence of the gazelles, you would insert a comma after grazed. But if you meant the gazelles were oblivious of the presence of the lions, you would leave the comma out.