What is the best way to sell this watch?
The easiest way to sell is eBay. You reach a wide audience and most things go for about what they're worth at auction, or if you think it's worth more than what similar watches sell for on eBay, then you can also set a fixed price.
The Phillipe Patek look alike goes for 7k- since this is Wilhelm what is fair value?
I'm afraid that a general similarity to a Patek isn't going to result in remotely similar prices. Really, only a fraction of vintage watches are particularly collectible. And Patek is about the most desirable of them all. For lesser brands and lesser known brands, there really isn't a comparison to be drawn. Also, ladies' watches are not as sought after as men's watches. There's just not as large of a market. More often than not, watches like these are valued mostly for their gold content and a modest premium for functionality and aesthetics.
Honestly, I think watches like this tend to sell on eBay for not much more than a couple hundred dollars. If the bracelet is also solid gold, then probably double it or more.
Given that it has a family connection, I'd probably consider keeping it. Just my two cents.