If she likes Arbor Mist, I bet she'd love those Island Mist kits. They are around $60 and make 6 gallons of a sweet wine. My friend has made mango symphony, and kiwi pear sauvingon blanc, but I've seen other flavors as well. It comes with everything you need, and she'd probably like it alot more than a traditional blackberry wine which uses a ton of berries and would probably need to be sweetened quite a bit to get the flavor she'd like.
I've seen a blackberry merlot kid (same brand) but I've never tried it.