The reason that you cannot claim the rewards is due to you having an identical IP address, though since you're mentioning your WiFi, you probably already know this, the system is in place to keep someone from making multiple accounts and getting massive amounts of daily rewards before sending it over to their main account, and if you really want to speak with a member of staff, i'd send a PM to someone like Ducks as they'd be the one to solve this, though chances are that they'd most likely not put a system in place just so that you and your sister can get some money. Money isn't even much of a big deal, as long as you don't sprint around everywhere, you'll almost never get hungry.. ..Or you could set up a system so that you two can split the money.