I know that except Sweta all the Khanna's are basically good people. But still they don't know Avni's true identity. So far they are impressed with Avni as a person but once they will come to know that Avni lied about her identity, they may think that she was faking goodness all this while with some hidden bad intentions. Ofcourse Neil will support her that time but the humiliation that she will have to face is unavoidable and it won't be possible for her to stay in Khanna house with so much of distrust and negativity around. What I understand is that Avni wants to stay with them because she received the love and compassion from them which she was craving since her childhood. But family bonds cannot be built on the foundation of lie and deceit.
Here I expected some foresightedness and clarity of purpose from Neil's side. Avni's life is already messed with too many problems to handle. That is why she is concentrating more on whatever little happiness she is getting at present without paying much heed to future. But Neil has always been clear-headed and logical in his approach. He wants to make Avni happy by celebrating her birthday but that is only a short term happiness.What about the future? It is Neil who has to take a firm decision whether he wants to stay with Avni or not because the only way Avni can stay in house is as Neil's wife. And for that he will have to give recognition to Avni as his wife which he can't give unless he stops giving excuses to Sweta regarding why he is doing anything for Avni. So I think for the time being Avni should leave the house and let Neil reveal Avni's truth to his family and take a firm call on whether he want to make Avni a part of his family or not.