Naughty Megan

Aiyooo. Megan now very very naughty and stubborn. If she was forbid to do something, she'll stomped her feet or throw something. She even purposely bang her plastic motor car or turn away from you.
Last night, I scold her because she refused to finished her milk before sleeping, I said: 'CinCin naughty, doesn't finish milk, mama bo sayang liau.' then I walked away. She knew I'm not happy with her, but she still didn't want her milk (she dined on 6.30 so, at 10.00 she must be hungry already). You know what she did? She ignored me completely. She just rolled and turned around her new bed (just bought her two days ago) and didn't make even a single sound which she usually will keep talking aka yayi-ing until fall to sleep.
Ohhhh.. my heart melt lah, can't bear to think that she'll fell to sleep in sadness because her mummy blamed her for not finished her milk (thinking again now, I wonder if she was sad at all) so, later I asked her gently : 'Cincin de jiau cai na li?'She quickly jump up from her bad and show me her leg, smiled so sweetly to me and kissed my cheek then she started ya-ya-ing again until fell to sleep.
Ohhh she can be really a sweetheart sometimes.
Do you think I need to be stern, set limit or discipline her? She is just 14 months.