Hindu Media Wiki

Santhoshi Mata has absolutely no basis in Hindu scripture. The earliest mention of her is in a modern-day Hindi pamphlet called the Santhoshi Mata Vrata Katha, which you can read here. In any case, there is absolutely no record of Santhoshi Mata before the 1960's, when her first five temples were stablished. Here's what this journal paper says:

Art historian Michael Brand traced the history of the goddess’ worship to the early 1960s, when five temples to Santoshi Ma were dedicated at widely-separated sites in northern India.

Also, these temples were not originally Santhoshi Mata; rather they were temples to other goddesses which were converted to Santhoshi Mata temples. Here's what this book says about the Jodhpur Santhoshi Mata temple:

In fact, although a temple to her existed in Jodhpur, Rajasthan, she had evidently not been known very long under that name or in that form even there. Before 1967 the temple now dedicated to her had belonged to a goddess called Lal Sagar ki Mata, "The Mother of the Red Lake," near whose banks it stands, and the characteristics of the earlier goddess diverged in important respects from those of Santhoshi Ma. Most significantly, Lal Sagar ki Mata was a carnivore, to whom goats and other animals were periodically sacrificed, whereas Santhoshi Ma is a vegetarian, with chickpeas and unrefined sugar at the center of her diet.

In any case, Santhoshi Mata was popularized by the 1975 movie Jai Santhoshi Maa, which also introduced the notion that Santhoshi Maa is Ganesha's daughter, something that's not even mentioned in the Santhoshi Mata Vrata Katha. For the record, the only children of Ganesha mentioned in Hindu scripture are his sons Shubha and Labha, there's no reference to him having a daughter.