The correct option is A am meeting
The given sentence states a future action, i.e., an action that is yet to happen.
This is suggested by the sentence: "She has made reservations..." which states an action in the present tense. (The reservation is made before going for dinner, so the action of 'going for dinner' will take place after, i.e., future.)
Option D: 'Am meeting' is in the present continuous tense. The present continuous tense (in the context of this sentence) indicates an action that is yet to happen. Hence D is the most appropriate option.
Option A: 'Met' is in the simple past tense. It does not refer to the future, hence A is incorrect.
Option B: 'Meet' is in the simple present tense. It indicates a daily habit, like 'I meet new people every day.'. It does not refer to the future, hence B is incorrect.
Option C: 'Going to meet' is incomplete without the verb 'am'. ('Am' is an important verb that indicates the first person singular 'I'. It is used in the present continuous tense. Also, it means the same as 'am meeting', but the verb is missing.) Hence C is also incorrect.