Going off [1] and [2], it seems like she was definitely a lone writer but it also sounds like a lot of them were 75-100 pages - "[in 1962, Bruguera] offered her a contract to deliver a 76-page novel every week. This she did until Bruguera's collapse in 1985" which makes 23 years of 52 novels or about 1200.

[1] https://www.theguardian.com/books/2009/may/04/obituary-corin... [2] https://en.wikipedia.org/wiki/Cor%C3%ADn_Tellado