You can do that as the strength of the perfume in the first place depends on the dilution.
You would have to have high proof vodka, but it would be best if you use perfumer's alcohol, which they sell at Snowdrift Farm.
Make sure you disinfect your atomiser first by boiling, or washing it with rubbing alcohol. Make sure you also do the same for your pippette.
Let's say the atomiser is 10ml. Dilute the current perfume slowly, adding 10-20 drops. Let it sit for a 2-3 days and come back to it. If it's a bit strong, add more alcohol. If it's not strong enough, add a drop or two from the perfume source.
Make sure you use a clean pippette each time to avoid contamination.