I’ve though a lot about this line and I think it means much more than I thought. For most of the musical, Eliza has been completely all right with going along with what other people tell or suggest her to do and if she’s not doing that, she is fixated on someone else’s actions. Don’t get me wrong, I’m not saying that that is all Eliza is capable of, she just seems very accepting and selfless for everyone else.
Take the first time we see her, she is following Angelica’s example and being excited about the revolution. Her solo part is simply reiterating something Angelica already sang. Then she meets Alexander, and yes, she loves him, but from that point on her appearances show her caring for Alexander and their children. When the Reynolds Pamphlet happens, she sings all about how Alexander has hurt her.
But this line from ‘Best of Wives and Best of Women’ is the first truly independent line we hear from Eliza. This decision is not based on or in spite of somebody else’s actions. It is after the Reynolds Pamphlet happens, after Philip dies, after all her heartbreak that Eliza finally does something purely for her. From that point on, she decides to do so many things, that are not all for other people.
In my opinion, seeing sweet Eliza do something purely for herself is the best bit of character development in this whole damn musical.