Power of Attorney Money Transfer

I have power of attorney for my mother and have a joint account with her credit union.  I transferred more than $15,000 from the joint credit union account to my joint account with my husband to pay her bills and keep the money in savings.  (I have had issues with credit unions and fees and have come to find out that banking laws are different for credit unions.)  Since the money I transferred was from a joint account with my mother and I have power of attorney, is this money considered a gift?  Inheritance?  Is this taxable and if so how do I file the tax?