All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
First of all, you must repent to Allah, The Exalted, and beware of what leads to Fitnah (temptation), like being alone with a non-Mahram (marriageable) woman, as it leads to committing sin. This is why the Prophet, sallallaahu ‘alayhi wa sallam, warned against it; he, sallallaahu ‘alayhi wa sallam, said, “Whenever a man is alone with a woman who is not lawful for him, the third of them is Satan.” [Ahmad]
Please refer to fatwa 86527 about the conditions of repentance.
According to the view of the majority of the scholars, this woman's daughter does not become unlawful for you to marry merely because of what happened of touching her mother's private parts or looking at it with lust. The Encyclopedia of Fiqh reads, “The Maalikis, Shaafi‘is, and Hanbalis held that looking at a woman's private parts does not establish the prohibition of marriage to her female descendants or ascendants (or her marriage to his male descendants or ascendants). Only the Hanafis held that looking at a woman's private parts with lust establishes such a prohibition of marriage.”
We hold the view of the majority of scholars as the preponderant one in this regard because there is no authentic evidence that clearly proves the prohibition of such marriage (marrying her daughter) because of these actions.
Allah knows best.