Ok, first off under no circumstance is it ok to release a pet snake into the wild. Ball Pythons come from a region in North Western Africa, they cannot survive outside in most other parts of the world. You need to make sure that your mother understands that releasing it will most likely result in a dead snake by the end of this year. Further releasing a non-native snake is illegal in many places and is morally wrong even if it is legal.
Big chain pet stores have a pretty bad record with reptiles, but it is still a better option than releasing it into the wild.
Most areas have exotic/reptile pet stores that have much more knowledgable staff than a shop like petco. If you have one in your area you might be able to do one of three things:
1. Sell them your snake
2. Be allowed to post a classified ad in their shop
3. Worst case they might be willing to take the snake off of your hands for free
You always have the option of posting an ebay ad.
Right here on BP.net we have a for sale/trade section
There is a website called kingsnake classifieds that you can sell a snake on
Fauna Classifieds also is a good place to sell a reptile.
Where do you live if you don't mind me asking? You don't need to be exact, just a state/city/etc will be fine, there might be someone here on this site local to you that could help you out.