Safety Measures

To avoid a repeat of Sil's mating rampage in the first movie, they take several precautions. They chemically repress Eve's instinct to reproduce and enforce a strict "no boys allowed in the lab" rule. For added security, they have an invisible fence with a bomb in her brain.... Anything else ?

How about we tie her tubes?? Though they repeatedly point out that she's half human, her clear function is that of a lab rat. She exists only to research defense against future possible alien attack. Such research wouldn't require a fertile subject.