Are you using them on the same Wifi/ IP server? Did you and your friend create accounts on the same IP server?
If it's the first option, try logging your account on your own wifi and their account on another server.
If it's the latter, there's no changing that because the accounts are now considered of one household. There is a rule in place that doesn't allow trading between household members. :)
Maybe Eve can help for the latter.
Winter Month: 3 
Night 
