Legal Question in Intellectual Property in Missouri

You need not fight it at all, if you are confident that the claims are baseless -- at least not until she actually sues. On the other hand, if she has threatened to sue, you could actually sue for a declaratory judgment. Or, perhaps a firm letter from your attorney in response would be education enough that the company leaves you alone. Weighing the best option is best done with the advice of your attorney. Not only can your attorney help weigh the legal options, but a good one will also help you look at it more objectively -- sometimes, having a right to sue is not a good enough reason to sue. Sometimes, ignoring a baseless claim could prove costly (even a fool can sue).

In the meantime, take a look at the trademark and consider whether the design they are complaining about is likely to cause confusion for a consumer familiar with the one registered by the complaining company (presumably, if it is a federal TM, they gave you a registration number, and you can look it up at www.uspto.gov). Have both their mark and your ruffle with you when you speak with your attorney so that the attorney can make an objective evaluation, because it will be hard to evaluate a mere description of "similar ruffles". (My guess is that most trademark lawyers would find it hard to imagine a baby shoe ruffle being used as a trademark, so showing them the actual trademark, and your ruffle in comparison, would be helpful.)