Sure. She's a chill, mellow, Venice Beach skater girl. Despite the chill demeanor, she has intense passion for her hobbies, and somewhat of a thrillseeking attitude (relatively speaking, obviously not as much as Star). She admires perseverance and looking beyond the exterior, so to speak. She's dorky when she needs to be, and she's reassuring without falling so far into the "teen mom" role; she still knows how to have fun. She may be a bit socially oblivious at times, but she's not dumb.
Or is that too many "positive" traits to warrant being called a personality?
People can also speculate about insecurity or being underestimated or how she feels about being double-crossed after Starcrushed, but that's purely speculation so I can't really count that.
None of this is like super deep or anything, and Jackie isn't a super deep character. But I'm tired of people saying she's so much less of a character than, say, Janna or Kelly.