Annichen Merchel/ Mærkel

She might be identical to the Anniken Mærkel in https://www.digitalarkivet.no/en/census/person/pf01058333003984

If so, she married a second time, Knud Mølbach. That Anniken Mærkel is mentioned in https://forum.arkivverket.no/topic/136852-51419-skienslektene-forbe.... According to that, she is the aunt of Anna Dorothea Sommer and hence the sister of Birthe Kristine Sommer. The family of her second husband is then probably the same Mølbach family into which her son Johan Georg married. The husbad Knud Mølbach was, according to the census data, aged 57 in 1801. This gives a date of birth 1744. There is a brother of the father of her son in law calle Knud, born in 1744: https://www.myheritage.de/research/collection-1/myheritage-stammbau..., on Geni Knud Sørensen Mølbach. This is probably her second husband.

If she is the same person, her year of birth would be 1738.