That's it, double flowered Hawthorn! I never realized it was a tree, looked like an overgrown shrub or bush. Love it! Thank you!

You might want to do some research on this plant. Purple loosestrife is considered a primary invasive species across much of North America and even cultivated forms are discouraged (they are no longer considered sterile). Lots of other great flowering plants could be suggested for replacement.

Instead of collecting seeds, she might even have some babies coming up in the soil beneath the plants why doesn't she try cutttings, procedure follows: Cherrylaurel hardwood cuttings can be taken any time the growth is firm which is generally June/July through to the next April. Use rooting hormone, a peat & pearlite rooting mixture and mist. Rooting should take place in 4-6 weeks. Make certain she mists daily or puts plastic over the container out of the sun and she could be a year ahead of schedule. Here is a link that might be useful: Propagating Perennials

Looks like one of the 'Knockout' series. I have two 'Blushing KOs' and can tell you some pros and cons. Con: They readily hit 6' by 6'. This is OK for me, but not OK if you want something that tops out at 3 or 4 feet. I don't know what kind of shape they would have if you tried to keep them pruned, but without pruning, they tend to have a pleasant shape with flowers all the way to the ground. They tend to produce quite a few stems where the flower color reverts to the screaming magenta of the first 'KO' variety. I don't much like that color, but it's a matter of taste. No fragrance. Pro: Without a doubt, Feature No. 1 is the robust health of the plant. Leaves remain shiny and fresh all summer long. No disease at all. Zero. The thing blooms all summer. A bit of a downer if Japanese beetles are a pest in your area, but really nice in the autumn. Mine bloom right into the cool weather. It holds foliage until well into the autumn, too. Foliage color on new growth is a nice, rich burgundy. It has thorns, but not really awful ones. It doesn't need a lot of special soil care. A couple of shovelfuls of compost or manure in the spring will do the job.