I think it was a typo. If they were her cats she wouldn't call them strays. I think the sentence was intended to be, "...brought about by stray cats visiting her yard." by not my.
Anyhow, I'm sure someone who would come to spray for fleas would not spray up high where the fruit grows, but along the edges of the yard, down low, where the fleas live.
There are a number of things she can do to get rid of the cats. Trap them and bring them to the pound. If she doesn't leave her address, they can't give them back. If she really doesn't want to argue with anyone about the cats, she can cut the loss of the cages and just leave them all caged in the front of the pound and drive away. They will probably be destroyed as in this economy I doubt there are many people looking for another mouth to feed but it's an option.
She could buy a dog. One dog in that yard will cause those cats to find new stomping grounds. They hang out there because they feel safe.
You could get motion activated sprinklers to place around and when the cats come in the yard they'll get squirt and leave. This suggestion was highly rated as being the most effective aside from buying a dog. Here is a link to a popular sprinkler: http://tinyurl.com/338ku5h
You can buy coyote or wolf urine. You can buy it as a spray. Hit the top and bottom of your fence and all around the perimeter and the cats should stay away. Needs to be reapplied after it rains.
You can lay chicken wire where the cats like to poop and it should deter them from hanging around.
You can get chicken wire and line the top of your fence with it to keep them from jumping over. Dig a little tunnel directly below the fence; two inches wide and six inches deep, then fill the tunnel with quick cement, this prevents cats from digging their way into your yard.
Invest in plants that are repulsive to cats. Naturally repel cats by planting peppermint, geranium, rue, lavender, garlic, lemon grass and thyme.
Repel cats with citrus; oranges, grapefruit, lemons and lime peel. Eat the fruit but keep the peels. Dice the peel into smaller pieces and place in your flowerbeds. Then toss the peel wherever you want, cats detest citrus. Only one problem, you will have to replenish your peels once a week.
Brew some coffee, enjoy a cup but do not throw away the grounds. Sprinkle coffee grounds in your yard and flowerbeds. Not only does coffee repel cats, it also keeps the raccoons, slugs and snails away.
I have no idea if any of these ideas will work as I've found them suggested all over the internet. The only one I have any confidence in is trapping them and leaving them at the door of a shelter so they can either be adopted out or destroyed.