[5][6] Her cousins were the sisters novelist and industrialist Amy Dillwyn and the lepidopterist Mary De la Beche Nicholl.

[3] Due to Llewelyn's interest in astronomy, her father constructed an equatorial observatory at Penllergare Valley Woods for her sixteenth birthday.

[10] She later recalled how "as moonlight requires much longer exposure, it was my business to keep the telescope moving steadily as there was no clockwork action.

[11] Collaboration between Llewelyn and her father also extended to meteorology, as they contributed to the maintenance and monitoring of the British Science Association's volunteer weather stations.

[16] In 1874, Llewelyn corresponded with Charles Darwin in the pages of Nature about her observations of birds biting flowers to eat nectar.