\!h Change using GRANT, without granting any extra privilages:
GRANT USAGE ON  *.* TO 'selina'@'localhost' IDENTIFIED BY 'new_pass'; -- overwritten old password

\!h Another way, using SET PASSWORD:
SET PASSWORD FOR 'selina'@'localhost' = PASSWORD('new_pass');

\!h Shorter if you're logged in as that user:
SET PASSWORD = PASSWORD('new_pass');

\!h Remove a password with SET PASSWORD:
SET PASSWORD FOR 'selina'@'localhost' = '';