Una likes tough, competent women, and as such, she really likes Peggy. They seem to be cut from a very similar bolt of cloth (resourceful, English, classy), and indeed have similar backgrounds—admittedly Una's been knocking around the Multiverse for much, much longer, but she's had a lot of life-during-wartime experience, just as Peggy has. She's definitely someone Una wants to cultivate as a friend and ally, and at some point they really need to go out for a drink or something.