Stolen MacBook Pro, encrypted with FileVault. Can they still access it because of a poor password?

My MacBook Pro was stolen recently. I had it encrypted using Filevault and it required my password for login after woken from sleep.

My password however is just a word of three letters, not abc, def or klm but more like tfj, ksa, ale, etc...

My question is this can they still access my files in any way? Via the guest access maybe or by breaking the password?

Greatly appreciate your answers.