She may have already shipped and did not update the status on ebay. But if you only paid on Dec. 28th. that is a Friday and she may not ship on weekends either.
Anyways it has only been 5 days since you paid and there was a weekend in there and then New Year's. So even if she did ship, let's say Saturday they would not be to you yet.
I doubt I would be concerned at this point. If you only emailed her yesterday it can take up to 24 hours for a seller to respond. I honestly would give it a bit more time because like I mentioned above, even if she did ship out already it would not be to you yet.