I'm pretty certain it's a Tradescantia species- the way the top two leaves nest within each other with the blossom growing from that is typical. Hard to tell from the image, but the flower looks like a pinker variety of day-flower, or spiderwort, which is a wide-ranging species with many variations in colour found all over the southern U.S and through Mexico. Some are invasive, and all grow like gangbusters if left to their own devices. They will self-seed readily, can be drought-tolerant, doesn't mind light shade to sun, could care less what soil it's in as long as it isn't sopping wet, though full sun in hot areas can stress it. Can look really sweet in a hanging pot. :-) All in all, a pretty plant, just be careful where you put it!