What do you do about a girl that likes you but you don't like her back?

Hi everyone, there is a certain girl who is my mom's friend's daughter whom is a few months younger than me and recently I had just found out that she likes me more than a friend. She admitted it over a text message and is really sad about it that I don't like her back. Please help me out guys, its bugging me lol.. I don't want to feel awkward around her, since she's my mom's friend's daughter, I see her often and I don't want to spoil the friendship my mom and her mom have with each other..