Anakin,
You might want to check this, but as Crete is a Greek island your wife would need to secure a Schengen Visa from the Greek Embassy.
Travelling together with a UK (EU) spouse means there is no fee and the procedure is simple and quick.
The European Commission expects under four weeks.
The questions marked with * on the form (employment,resources,itinerary,medical insurances etc.) do not need to be answered.
The entire form is only three pages long.
Usually, you can expect a 90 day visa with six month validity, sometimes the validity may be longer with 5 years being the maximum. (Always maximum of 90 days in a six month period starting with first entry.)
The reason I suggest checking is that there's been a lot of talk recently about Greece being excluded from the Schengen Treaty