Character Analysis
Tanis is a widow who's younger than Babbitt, but not super young. She becomes Babbitt's mistress when Babbitt decides to lash out against his boring life and have an affair.
One of the first things we know about Tanis is that she is very concerned with always being "feminine," as she openly criticizes "these women that try to imitate men, and play golf and everything, and ruin their complexions and spoil their hands!" (4.2.16). This kind of femininity is just what Babbitt's looking for, since he is sick of hanging around a wife who doesn't bother to put on red lipstick, stilettos, and pearls around the house.
But just because Tanis is femmy-fem-fem doesn't mean that she's a pushover. At one point, she and Babbitt decide to eat dinner together in her apartment. When Babbitt asks her if she'll put on a sexy dress, she replies,
"I'm going to dine just as I am, in this old chiffon rag, and it you can't stand poor Tanis that way, you can go to the club for dinner!" (28.1.89)
So there, Babbitt. Just because you're going through a mid-life crisis doesn't mean the world is going to start doing your bidding.
As Babbitt's affair with Tanis progresses, we begin to see the more insecure side of Tanis. She becomes more and more afraid that Babbitt will leave her and that she'll be left all alone. When Babbitt fails to call her for a few days, she even calls him to remind him,
"You know I'm terribly ambitious for you; much more than I am for myself. I just don't want you to forget poor Tanis." (31.1.6)
Pro-tip for dating: don't refer to yourself as "poor" all the time. Tanis doesn't want to hold Babbitt back from doing what he wants… but she also doesn't want him to forget her. Unfortunately, though, that's exactly what he does.
Tanis' Timeline