Snailshell doesn't really fling. A buck needs to join her harem to breed with her. Unless he is an acha, Snailshell will consider a fling for acha.
Snailshell is also open to mock breedings with other ladies because it'd make her proud to know the Motherfather used her to create new kin.
A buck joining her harem does not need to be monogamous, but he cannot be involved in romance or breedings with one of Snailshell's family. Non-family tribe members are ok.