She is an energy-sucking leech, she attaches herself to a host body then uses their energy to attract her next victim and so on (either via mouth to mouth or through the victim's clothes). If she hides on a human, that human would be extremely active, have low energy, moves slowly, but come alive at night for feeding.
Her body can be separated into two (or possibly more), to give at least one of them the chance to escape, attack, hide, or control more hosts, etc. So the only way to capture her is using the special bottle 71, trapping her within the bottle from escaping.
Fred is the only known host that was able to resist her control.
When Slimetra was in Fred's body, all of the girls were mesmerized of Fred's increased attractiveness except Braianna, which is still unknown.