Undoubtedly, your Excel workbook will also be showing FALSE, since the formula leaves the false result undefined. It should be something like:
=IF(A1="sn","sherri brooks","")
In any event, you don't need to use that column in your mailmerge; Word can use field coding to do it's own testing directly. Such a field might be constructed along the lines of:
{IF{MERGEFIELD Initials}= "sn" "sherri brooks"}
or
{IF«Initials»= "sn" "sherri brooks"}
without the need to address the FALSE condition.

Note: The field brace pairs (i.e. '{ }') for the above example are all created in the document itself, via Ctrl-F9 (Cmd-F9 on a Mac or, if you’re using a laptop, you might need to use Ctrl-Fn-F9); you can't simply type them or copy & paste them from this message. Nor is it practical to add them via any of the standard Word dialogues. Likewise, the chevrons (i.e. '« »') are part of the actual mergefields - which you can insert from the 'Insert Merge Field' dropdown (i.e. you can't type or copy & paste them from this message, either). The spaces represented in the field constructions are all required.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]