Use 'cutesy' to describe something that is excessively or inappropriately cute to the point it is annoying. Her cutesy remarks during the meeting were not well-received.
Pro Tip 2/3
Possibly Patronizing
'Cutesy' can suggest that the person is not taking the other party seriously and can be patronizing. Talking in a cutesy voice to adults can seem disrespectful.
Pro Tip 3/3
Informal Contexts
'Cutesy' is casual, best used in informal settings and often avoided in serious or formal discussion. Using a cutesy tone in a casual chat with friends is fine.