It's no wonder Linda is cool, with Aunt Martha for a grandmother. She's so beloved in her community—by blacks and whites—that, when Dr. Flint puts her up for sale after her mistress dies, no one will bid for her except a teeny old white woman who immediately sets her free.
Once free, Aunt Martha sets up shop as a baker. She earns a good wage and manages to keep her big family fed and clothed, and eventually buying some of them free. Plus, even though Aunt Martha was "so faithful" as a slave (1.1), once free she is one fiery lady. She even stands up to Dr. Flint, telling him, "Get out of my house… Go home and take care of your wife and children" (15).
Even more than setting them free, Aunt Martha wants to keep her children together. Which is great, of course, but at times it seems like this attitude is really holding them back. It's obvious that Aunt Martha is a huge source of spiritual (and physical) comfort to Linda, but she also guilt-trips her about trying to run away:
Stand by your own children, and suffer with them till death. Nobody respects a mother who forsakes her children; and if you leave them, you will never have a happy moment. If you go, you will make me miserable the short time I have to live. (16)
If you think about it, it almost seems like the crawlspace could be a metaphor for how Linda feels about her grandmother's advice: she suffers physical, bodily imprisonment to stay near her children. Aunt Martha might improve, but it causes severe and lasting physical effects. You have to wonder if it was worth it.
And when Linda does get a chance to escape, her grandmother almost convinces her not to go.
My grandmother, always nervously sensitive about runaways, was terribly frightened. She felt sure that a similar fate awaited me, if I did not desist from my enterprise. She sobbed, and groaned, and entreated me not to go. (29)
We hate to say it, but this sounds like some serious emotional manipulation. Aunt Martha even claims that it's going to kill her if Linda leaves. What she doesn’t seem to understand is that it's killing Linda to stay. Aunt Martha may value freedom, but she doesn't seem to see slavery as the same kind of moral and psychic burden that Linda does.
Aunt Martha is a source of inspiration for Linda, but she's also a cautionary tale. If Linda's fate had been different, she might have ended up like Aunt Martha: enslaved all her life, and carrying the mentality of slavery even into freedom.