I feel like as someone in your late twenties/early thirties you definitely know what your mom intentions were.. can't have you go one upping the other kid, probably didn't trust you enough to not go full blown mozart on the other kid.. That would probably cause strains in the relationship with her boss and colleague at work. The mom could definitely have explained this to Enna afterwards when they are alone but not letting her play was the right thing to do at that moment.