（答好了有追分）双宾语改写成被动语态的问题

（答好了有追分）双宾语改写成被动语态的问题
1 He gave her some money.他给她一些钱.
→ She was given some money.
→Some money was given to him.
2 He bought her a watch.他给她买了一快表.
→ A watch was bought for her.
→She was bought a watch.
像这句 为什么 第一句改写后会用到to 而第二句改写后会用到for 为什么呢?