First Question : Did you write up a contract? If yes did you both sign it? If yes is it notarized?
If yes to all three...you are 'cheating', and you need to tell the person that you are launching the business without them because you did all of the work and you are ready to go. Tell them that due to this they will only have a 25% stake in the business, and that is only because they are your friend.
If no, you are not cheating but your friend may think so...so once again say " I did all the work and I am ready to launch without you, and I plan to do so. Do you still want to be a part of it? if yes, it will be best for us if we draw up and sing an agreement about how much work you will do, and how much of the profit you will get for that work.
If this is not a close friendship...then it does not matter...just go ahead and do what you want to do.