I got you. My wife was a swimmer and has mentioned numerous times how nice it would be to have a lap pool in the back yard. I just keep quiet and it dies away.
I casually know a few hard core swimmers who are friends with a former co-worker. They do mini and full triathlons and are between 35-50 YO, most of them were talented college swimmers or track competitors. They all train at a facility with excellent coaches, I don't think they could stay motivated in a pool in the yard. 3 of them competed in the Ironman a few weeks ago and did pretty well. If there is a local club or facility that might be worth her checking out to see if it meets her goals. Anyway, 6 months of that would be a heck of a lot more cost effective than a pool. Here is a link to the local club in ATL if interested for ideas: Dynamo