Does expiation become obligatory for someone who put perfume on her face covering and then changed it, and did not shorten her hair until after leaving the Haram, and put on the niqab while she was still in a state of ihram, despite knowing the rulings but forgetting them?

It is not permissible for a pilgrim in the state of ihram to apply perfume to their clothes or body after entering ihram. Among the prohibitions of ihram specific to women is covering the face with a niqab. What is prescribed for a woman is to uncover her face, unless non-mahram men pass by her, in which case she should cover it with something she lets down over her face. If a woman does this out of forgetfulness, there is nothing upon her.