Is it possible to lengthen the columella?

It is hard to make any recommendation with out seeing the pictures, the short columella can be lengthened by different techniques. 

Without photos and preferablya  review of your preop and post-op photos I could  not fathom a guess other than saying "maybe."

It is possible to lengthen the columella and typically requires the use of cartilage grafts. The cartilage is typically taken from the nasal septum, or if you don't have usable cartilage from your previous surgery it is harvested from the ear. This is something that is typically done under general anesthesia but depending on the amount of work that needs to be done can be modified accordingly. Make sure that you obtain consultation with a rhinoplasty specialist so that the problem can be addressed and treated appropriately.