"She changes her coat."
Translation:그녀는 코트를 갈아입어요.
옷을 갈아입다 is the common idiom used by Koreans to mean "to get changed"
[ vs. 옷을 입다 is "to get dressed"]
옷을 바꾸다 is used sometimes but my impression is that it indicates a change of clothes in the sense of exchanging, switching clothes (e.g. changing the type of clothing to suit each season).