Reply for non filling itr

Reply for Non filling ITR - verification issue NIN03 (My mother recently got a email from Income Tax about Non filling of ITR. She being a house wife never filled ITR. Last year my father made some investment on her name in Mutual Fund from his retirement money. IT dept tracked this transaction and is asking to fill ITR. There is no capital gain on the investment as such as there is withdrawal of the money. How can this purchase be shown in ITR if there is gain as of now? Also, how can the money source be shown in ITR?)