Take your one peaceful female out and leave her in a drum bowl or a plastic gallon water jug with a little of the top cut off... for protective custody? Then catch out the others. :)

Are the aggressive females' gravid spots round or oval - irregular in shape? If oval or irregular, they might be Gambusia. G. affinis and G. holbrooki are very aggressive. Do the aggressive females have clear fins? Does the non-aggressive female have color in her fins??

There are some neat Gambusia but those mentioned above (from the Eastern US) can be bad actors and their females can be easily confused with guppy females.

Did you get your guppies from a shop's feeder tank? That is a temptation because they are so cheap (and unfortunately often diseased). "They" often toss Gambusia in as feeders too.

Could you catch the aggressive females? If they can be identified, catch them, bag 'em up and return them. Watch the remaining pair - they may get along fine. More tips on that next comment.

Other considerations: How big is your aquarium? How is it decorated? What temperature is it at? How long has it been set up? When did you last do a partial water change?

If yours is a brand new, recently set up 10-gallon aquarium (say in the last six - eight weeks), you should start with maybe only one pair of guppies anyway. (For more on this click on the Immediate Help link to the upper left of this page. Please especially read through the section on New Tank/Cycling/Setting Up/Water Changing.)

Have you talked to your fish seller? What thoughts have they offered? Will they take back incompatible fish?

Do not throw any unwanted aquarium fish in any local water way. Local fishes are in trouble enough without having another aquarium disease introduced into their company. :(

I look forward to your answers on the nature of your aquarium and what you decide to do? Please respond. I promise to respond in turn and vote to put your post on page one. ;)