I have been looking for a female Combee for 2 days now on Route 12 in Pokemon Black 2.
Please help, I am trying to get a Vespiquen.
No, you aren't. Combee only has a 12.5% chance of being female. A quicker way to get Vespiquen is to go in shaking grass on Route 12.
Look at this link.
Combee really isn't that rare though, it has a 50% chance of appearing.
It's weird how you are taking 2 days and it took me 2 minutes.
Combee has 12.5% chance of being Female.
As I commented, your best bet is to search for Shaking Grass where you can directly get a Vespiquen without having to evolve it.