If it's minor, keeping up with regular trimmings with a good farrier could easily be enough to keep her straight. I had a mare that was poorly trimmed and shod for several years before we got her, causing her legs to all become crooked. It took our farrier almost two years, but he was able to correct most of the damage and make her reasonably straight again. A good farrier is worth their weight in gold. It would be hard to say if it's a conformation fault or not without pics. It could be, (you said she was a filly?) sometimes when they are young, everything is growing so fast that things get a little out of balance occasionally. Don't panic until you talk to the farrier.
"Keep a leg on each side and your mind in the middle"