Spam filtering for one user, but not another?

[BoxOfSnoo]

I have a couple of mailboxes on one domain, and in mine the spam filtering is awesome. After a little tweaking it gets everything with almost no false positives.

For my second user though, it seems to filter *nothing*. Several dozen spams a day come in to her mailbox. I looked at the headers and it looks like SpamAssassin is grading and tagging them, but no filtering is taking place. I am training SA every night on each relevant IMAP mailbox.

I can't figure out why such a difference on the same domain - under the same unix user account, with the same permissions, and the same configuration files.

Where should I look to see what is happening here? SA? Exim? Dovecot?

Thanks in advance.