Talk to pay pal and get their advice. If you do decide to send it, insure for the full value and maybe take it somewhere to be professionally wrapped and sent. Then you would have a witness and it wouldn't be just your word. Hummels are highly collectable, so I am not surprised that bidding went that high. You might want to get it appraised before sending it anywhere and insure for either the amount that you sold it at or the appraised value.
In the event that she does leave negative feedback... I don't know about others, but I look at negative feedbacks to see if it looks like a legitimate complaint (I keep in mind that some people just can't be pleased). Next I look for the sellers response. Did they lash out or handle it politely and courteously? If they put something like 'loser, I told you that there would be a delay', I don't want to deal with them. So make sure that any reply that you leave is polite.
Sending a tracking number to her doesn't mean anything. I 'won' a bid on a chainsaw that DH liked. The 'seller' sent me a tracking number that kept coming up as invalid, though with USPS that isn't uncommon (I have sent packages with a tracking number and had it show invalid number). The 'seller' claimed he shipped the item right away, but didn't send a tracking number for a week. I filed a claim with paypal, about two weeks later I got all but $25 of the money back. I left neg feedback and about three other people did at the same time, all on chainsaws that were listed as 'selling for a friend who has gone out of business'.