first instantiated SimplePie object cosumes 5mb?

This is a known issue. It is caused by a bug in PHP 5.2 and is fixed in PHP 5.3.

You need to manually call the destructor method before unsetting the $feed and $item variables.

source

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)