The Kinsey scale attempts to measure sexual orientation, from 0 (exclusively heterosexual) to 6 (exclusively homosexual). It was first published in Sexual Behavior in the Human Male (1948) by Alfred Kinsey, Wardell Pomeroy and others, and was also prominent in the complementary work Sexual Behavior in the Human Female (1953).
Here's the scale:
0 Exclusively heterosexual
1 Predominantly heterosexual, only incidentally homosexual
2 Predominantly heterosexual, but more than incidentally homosexual
3 Equally heterosexual and homosexual
4 Predominantly homosexual, but more than incidentally heterosexual
5 Predominantly homosexual, only incidentally heterosexual
6 Exclusively homosexual
Beth likes to have sex with men and women. I guess that would make her around a 3 on the Kinsey Scale?