You should check again the use of the Present Perfect Continues tense. Unfinished actions 1: To say how long for unfinished actions which started in the past and continue to the present. We often use this with 'for' and 'since' (see the the present perfect simple page for more about 'for' and 'since'). I've been living in London for two years. She's been working here since 2004. We've been waiting for the bus for hours. This use is very similar to how we use the present perfect simple, and often it's possible to use either tense. Of course, with stative verbs, we can't use the present perfect continuous. I've been here for hours. NOT: I've been being here for hours. 2: For temporary habits or situations. The action started in the past and continues to the present in the same way as with use number 1, but we don't answer the questions about 'how long' so clearly. Instead, we use a word like 'recently'. I've been going to the gym a lot recently. They've been living with his mother while they look for a house. I've been reading a lot recently. This is very similar to the use of the present continuous for temporary habits and often either tense is possible. Finished actions 3: Actions which have recently stopped (though the whole action can be unfinished) and have a result, which we can often see, hear, or feel, in the present. We don't use a time word here. I'm so tired, I've been studying. I've been running, so I'm really hot. It's been raining so the pavement is wet. The present perfect simple has a very similar use, which focuses on the result of the action, whereas the present perfect continuous focuses on the action itself.

You should analyze the situation, not only with the key worlds. All types of Continuous tenses emphasize DURATION of the action. It means that the most important thing about the message is the sentence is the duration. 1. She has not been attending lessons for some time now. Actions which have recently stopped (though the whole action can be unfinished) and have a result, which we can often see, hear, or feel, in the present. We don't use a time word here. - in the past (we don't know exactly when) she was attending - at some point in the past she stopped - the action of 'stopping' continues up to the present and has a result -> she is not here now 2. Come in, I have been expecting you. It simply means that when the person arrived, the locutor knew that the person  was supposed to be coming. Accordingly, the locutor expected to see this person walk through the door at any moment. The locutor was in a continuous state of expectation, hence "I have been expecting you". sutuation: - the person was expecting someone for some time in the past - time is not stated - the result of expecting the person -> the person showed up, yiu can see him/her and you can tell him/her "I've been expecting you"

The statements have a "present" context 1) "now" ... so the only reasonable answer is "she has not been attending lessons ... (and is still not attending)" 2) "come in" ... I have been expecting you (until just now when you arrived at the door)