I've made sour cherry wine, and it's good, but probably not what you're looking for. Once the sugars in cherries ferment out, it's TART!
What about one of those Welch's or Old Orchard Juice blends, like cherry/apple/raspberry or one of those? They would still ferment out and be tart, but you could either add non-fermentable sugars and bottle carb, or stabilize and sweeten (but no carbing).
If you are really serious about making something she'd like, and don't mind spending about $50 for 6 gallons, those "Island Mist" wine kits are really good. I'm not a sweet wine cooler type of winedrinker, but my best friend has made several and they are really good. She made Kiwi Pear Sauvignon Blanc, and Mango Citrus Symphony, and a couple of others I can't remember right now. They aren't carbed, though- there are stabilizers in there to prevent the sweeteners from restarting fermentation- but you could keg them if you wanted fizzy and had a kegging system.