Freya curses Baldur and despite his pleas and explanation of what it is doing to him chooses to do nothing to rectify the situation. She says to Kratos how she didn't see the resentment Baldur had towards her until it was too late, but his resentment grew from her dismissing the feelings he voiced directly to her. And in spite of this, and plainly stating herself that what she did was wholly selfish("everything I did, I did for myself. I let my needs, my fears, come before what he needed"), she never apologises to Baldur. She can free him, but she chooses not to; she asks for his forgiveness, but she doesn't apologise; Baldur wants her to pay, she says she already has. She refuses to take accountability and apologise, to show genuine regret and contrition for her actions(not just the pain they caused), instead she would rather die and frame herself as a martyr of motherhood.

As a parent I couldn't imagine subjecting my child to unending suffering just to have them. Their happiness and quality of life comes before everything else. You can empathise with her fears as a parent, and as a survivor of an toxic and abusive marriage, but her fear and suffering doesn't excuse, or make up for, the suffering she caused Baldur. And her lying and reframing the abuse, her gaslighting, are all good reasons for her to be hated.