给 can replace 向 when 向 is used with people and verbs. 给 cannot replace 向 when 向 is used with direction. Examples: – 我们必须向/给他们道谢。 wǒmen bìxū xiàng/gěi tāmen dàoxiè. We must say thank you to them. / We must thank them. – 她向/给老师道歉。 tā xiàng/gěi lǎoshī dàoqiàn. She apologised to the teacher.