In this case, it's figurative. Rounding the bases in a literal sense would be to touch the bases in a game of baseball. However, in a figurative sense, the bases represent different levels of intimacy with a romantic partner. For some idea of what they are, here's an excerpt from Wikipedia, Baseball metaphors for sex,
Among the most commonly used metaphors are the bases describing levels of physical intimacy (generally from a heterosexual perspective). Definitions vary, but the following are typical usages of the terms:
- First base – mouth-to-mouth kissing, especially French kissing;
- Second base – skin-to-skin touching/kissing of the breasts; in some contexts, it may instead refer to touching any erogenous zones through the clothes (i.e., not actually touching the skin), or manual stimulation of the genitals;
- Third base – touching below the waist (without sexual intercourse); in some contexts, it may instead refer to oral stimulation of the genitals;
- Home run (home base or scoring) – "full" sexual intercourse.
So, she knew that she would not win the man because she withheld sexual intimacy from him. Ultimately, I think she's suggesting that she lost because she wouldn't let him have sex with her ("home run", "scoring"). This is often considered a significant reason to end a relationship.