Normally inmates are allowed one package a quarter. Rarely inmates will use another inmates name and information to receive more pckages. With that said more times than not they are either paying of a debt, being forced through threats or intimidation to send the package to another inmate. If she has become extremely angry over the incident she you can rest assured it is not for her personal use. If anger doesn't work, she may come up with a story that she thinks will force you to do it, or she will try to contact another relative/friend to send the package. either way it is a violation of the rules and regulations.
You know your niece, so your gut feeling is more than likely correct.
Hope this has helped, let me know how it all turns out.
Terry B. Davis