Semen on a fast?

This is an embarrassing question but if a female fasts and she engages in intercourse frequently on her fast does having sperm internally (not in the mouth) compromise the fast? Isn't she feeding off it in a way? the reason is that afterwards there is always a very prominent increase in energy, vitality, happiness... and more or less the fast is miserable and unbearable without it.
Is this not really a Water Fast but a semen fast? if there is such thing?