After you have read the little bit below, please go over to the Google search box, click on www.guppylog.com, type plastic rug mesh in the open space and do a search for other discussions related to this topic. Oh - and read them over. ;)

You still haven't mentioned the size of your aquarium and it is difficult making recommendations to you. But let's assume that you have a 10-gallon aquarium. They are roughly 10 inches wide and 12 inches high. For a real quick fix stop at a crafts store. Perhaps call Michaels on the phone. See if you can buy a piece of that plastic rug mesh which would be 12 inches high and 12 or 13 or 14 inches wide. You should be able to insert that in your aquarium. The tension from the  bend in the 12 or 14 inches should hold the piece in there, unless there water's current is really strong. (You haven't mentioned what kind of filtration you have either, have you?)

Anyone else reading along can measure their aquariums and purchase an over-sized width for their tank and avoid some stress on a harassed fish. Because of the temporary nature of the arrangement, guppy and killifish clubs may have shows where the pairs are placed in critter keepers or 2.5-gallon tanks. They often have a box of those plastic mesh rectangles. A number of battered fish, often females, have been rescued from their partner by the hurried insertion of a mesh rectangle. A couple of us fairly frequently go on divider patrol.

They are a temporary solution. They will come loose - gravel is helpful in holding them in place. Also, fish will jump over the tops of the mesh from time to time. So keep an eye out.

And never use them to divide fish, which you absolutely do not what to have breed with each other. Murphy's law being what it is, that will be the tank that always has a jumper. ;)

Certainly there are also better and more expensive tank dividers, which you can purchase at some pet shops or order on-line. And if you read those threads from the search, suggestions are given for a more permanent tank divider using that plastic rug mesh. None of the dividers are completely fool-proof in separating fish though.

My lady says that the plastic rug mesh isn't as commonly promoted as it used to be. I think though that you still should be able to find it.

Place your overly enthusiastic males on one side of the mesh and your female on the other. Still have some hiding places (plants, plastic plants if they are not too horribly garish, rocks or even plastic "stuff" like Lock Rocks) for her.

Some of that "structure" can be had inexpensively in the few garage sales which will still be held this summer. I just finished bleaching and dechlorinating a bunch of plastic plants, which we got from a garage sale and a lot of them at the tail end of a fish auction for a dollar a bag. They are not my first choice for aquarium decor, but in "flashlight tanks" and even worked in with real plants in modestly lit aquariums, they can be very useful.

If you can't get a divider, do you have a clean bowl (another garage sale special) or soap-less gallon, wide-mouthed pickle jar? On a temporary basis (and they tend to become permanent) you could sequester the female there. Every day or two drain all of her water and change it with 98% from the tank she used to be in.

I'm sure that you are busy. If you are still a student type or a parent with kids, it might be to your advantage to check around for that mesh while you still might have a little more time this week. (I hear a resounding "HA!" from students and parents.)

A divider does not make an aquarium more attractive. But it might do wonders for your female guppy. :)