Explanation

The given sentence is an example of an optative sentence which expresses hope, prayer or wish. Following rules are followed to change the direct speech of such sentences:

If the reported speech starts with 'may', then the reporting verb 'said' is replaced with word 'prayed'.

The sentence becomes an assertive sentence.

The exclamation mark is omitted. 

The sentence would become - She prayed for a long life for him. 

Thus, option C is the correct answer according to the rules.