Certified isn't the best way to send packages. You can send it USPS priority, signature required, but it's usually not a good idea to require a signature unless the amount of the item is over $750. Ebay and Paypal will take a normal delivery confirmation as proof of delivery. They only require signature if the amount is over $750. When you require signature, lots of bad things can happen. The mail carrier can forget to get the signature when he delivers the package so tracking will never show it as delivered. The mail carrier can decide he doesn't want to wait for the signature, so he may forge it. The recipient may never be available to sign so the package gets returned to you.
UPS is usually a little better about getting a signature, but if the recipient isn't available within 3 tries, the package will be returned to you and you'll have to pay extra to get it back.
I'm using our business account I'm taking photos of the pkg at the ups store and when delivery is confirmed. At this point I'm over her and in 7 days I will report her to eBay [emoji20][emoji20][emoji20]