Aeltjen Hendrix van Heerden Hendrix - patronym and surname

Let me give some input from a Dutch perspective.
'Hendrix' (or Hendricks) is most likely Aeljen's patronym (after her father's first name). Many people in the Netherlands around that time had no surname but just a first name and patronym. On the Dutch part of Geni the patronym is placed in the second name field (and not in the surname field).
Women in the Netherlands never take on the surname of their husband, so she will have never been officially recorded under 'van Heerde'. If someone finds differently, then please add a source, but be aware that anohter internet tree is not a proper source.
I hope this is helpful.