Was there a traffic drop too, or just the sales? If you still have good traffic then try cross promoting other relevant products to the same audience. It doesn't have to be just about the lipstick...
Ah, yes, the power of MySpace...lol. You must be new to the internet.
So, in response to the original question "Is Wordpress good for ecommerce?" your answer is what??
You have to do a lot of research, reading and testing and be prepared to lose money, as most newbies lose money when they start off before learning from their mistakes.