Answer:
'mi hermana cocina muy bien'
Step-by-step explanation:
concina, because she is a female and you use the verb cocinar to say cooking.
cocinamos= we cook
cociana =she cooks
Also because she is a female and for females, you would use a feminine ending, hence 'a'. Which is used at the end of the word cocina.
ps. you spelt 'muy' wrong.
the correct sentence is 'mi hermana cocina muy bien'
which means 'my sister cooks very well.