I did find the record for Jannetje Leend.(ertsz) van der Borst's burial, on the 25th of January, 1763, in Poeldijk, here:
"Netherlands, Zuid-Holland Province, Church Records, 1367-1916," images, FamilySearch (https://familysearch.org/ark:/61903/3:1:3QS7-89QV-SG2F?cc=2037907&wc=SMMP-829%3A345830201%2C345993701%2C345995101 : 21 August 2014), Rooms Katholiek > Poeldijk > Dopen 1740-1812 Trouwen 1740-1811 Overlijden 1740-1812 > image 183 of 409; Rijksarchiefdienst Nederlands, Zuid-Holland (Netherlands National Archives, Zuid-Holland).
I'll keep looking for the baptism though.
I think it would be worthwhile to add Jannetje's profile in the meantime, as there are primary sources for her death, burial and marriage, as well as children.
I also wonder why her baptism is listed as 1730, it just doesn't sound feasible. I've searched the baptisms of Poeldijk 1693-1696 to no avail, and there aren't baptisms available for that date for either Nieuweveen or Nootdorp, I think the baptisms would have been registered in a larger parish. The problem is finding which one. I'll keep searching though.