Why are fanpop acounts temorarly disconected?

With all due respect, did your friend happen to have multiple accounts? When multiple accounts are discovered on the same IP address, sometimes that IP address (and subsequently any user accounts which used that address) can be blocked. If your friend was blocked by accident (IE, maybe siblings have been using the computer and/or creating extra accounts), then s/he should DEFINITELY link in order to remove the block. Have him/her tell them the user name, and the F4 will look into it.

maybe she was banned?

I would also guess that she was banned, try asking one of the Fanpop 4 (Dave, Papa, Michael and Cliff), just give them a private message or try "Contact Us" which is at the bottom of every page on Fanpop and ask about it, remember to mention the fan's username in the message, they probably have some form of records to find out why. And if they weren't banned, you'll probably still find out what happened.