It didn't seem like she had the purple lightning thing going on as liberty (and if she had, wouldn't people have figured out they were the same person?)
So how did her power change when she became Stormfront?
Well. A-Train isn't the only superspeedster. And if there are several speedsters, based on the data we have on the show - the logical conclusion is that powers aren't unique. Perhaps Homelander, but he's special now ain't he?