did she loop right after killing it? or when she died later on? because its an important difference in the mechanics.
if she looped by just killing it, i.e. she kept her memories on a loop triggered by the alien death, not her own, it means all people (and aliens) that have this ability keep their memories no matter whose death triggers the loop. that means even tho rita or mc may be getting stronger in the loops or adapting their strats, so can the aliens, using the same loops that you're triggering instead of needing their own.
on the other hand, if the one that dies is the only one to keep their memories, dying first somehow becomes a winning strategy... which is a bit of a contradiction when your goal normally is to survive and kill them. if the other team takes notice of your ability, they can still send info about it in to the past by suiciding before you die. this mechanic becomes a real clusterfuck and blows away any logic if both sides have it.