Mother in law nick naming my son

So I am 23 weeks pregnant and we are naming our baby boy Dexter Cash and my husbands mom has been calling him DC. It bugs the living crap out of me and she told me she'll never call him by his name only DC because she hates his name she thinks it's ugly. Anybody have this problem and how did they solve it ? Ive been biting my tongue but with me being as moody as I've been it won't be much longer until I freak !🙄😳