Is this the same nun in these sutta references? From sutta SA 2.218:

The renunciant Gotama is staying at Sāvatthī at the Jeta Grove in the
Anāthapiṇḍika Park. And there is the nun Selā who took her robes and
her begging bowl and entered Sāvatthī to beg for food. Having finished
her meal, she cleaned her bowl, gathered her seat and has gone to the
Andhavana forest. I shall disturb her!” Having thought this he changed
into a young man, approached her and spoke a verse:
“Who is it that created beings,
by whom were they made?
Why are they called beings,
from where do they arise?”

That time the nun Selā, having heard the verse thought: “Who is this?
What a cheat! Is he a human or a non-human being?” She entered
concentration and recognized he was King Māra. She answered with a
verse:
“Māra, you have a wrong view of ‘beings’,
saying and believing they actually exist as substantial entities.
Conventional, empty they are but compounded entities
there are in fact no ‘beings.’
Like when causes and various conditions
converge and yield the use of a ‘chariot’.


From sutta SN 5.10:

Then Māra the Wicked, wanting to make the nun Vajirā feel fear,
terror, and goosebumps, wanting to make her fall away from immersion,
went up to her and addressed her in verse:
“Who created this sentient being?
Where is its maker?
Where has the being arisen?
And where does it cease?”

Then the nun Vajirā thought, “Who’s speaking this verse, a human or a
non-human?”
Then she thought, “This is Māra the Wicked, wanting to make me feel
fear, terror, and goosebumps, wanting to make me fall away from
immersion!”
Then Vajirā, knowing that this was Māra the Wicked, replied to him in
verse:
“Why do you believe there’s such a thing as a ‘sentient being’?
Māra, is this your theory?
This is just a pile of conditions,
you won’t find a sentient being here.

When the parts are assembled
we use the word ‘chariot’.
So too, when the aggregates are present
‘sentient being’ is the convention we use.


And from Mil 3.1.1:

Very good! Your Majesty has rightly grasped the meaning of “chariot.”
And just even so it is on account of all those things you questioned
me about— The thirty-two kinds of organic matter in a human body, and
the five constituent elements of being—that I come under the generally
understood term, the designation in common use, of “Nāgasena.” For it
was said, Sire, by our Sister Vajirā in the presence of the Blessed
One:
“Just as it is by the condition precedent
Of the co-existence of its various parts
That the word ‘chariot’ is used,
Just so is it that when the Skandhas
Are there we talk of a ‘being.’”

Most wonderful, Nāgasena, and most strange. Well has the puzzle put
to you, most difficult though it was, been solved. Were the Buddha
himself here he would approve your answer. Well done, well done,
Nāgasena!


Are these verses about the same nun? Is there anything more known about her?
They seem to be two different persons.
Info on Vajira Theri:

Vajirā Therī. The Samyutta Nikāya (S.i.134f) relates that one day, when she was taking her siesta in Adhavana at Sāvatthi, Mārā
questioned her as to the origin of “being&quot; (satta), its creator, its
origin, its destiny. Vajirā answers that there is no such thing as
“being,&quot; apart from certain conditioned factors, like a chariot, which
exists only because of its parts. Māra retires discomfited.
Vajirā's verses are often quoted (E.g Kvu. 240, 626; Mil. p.28;
Vsm.ii.593) both in the Canon and in later works, but they are not
included in the Therīgāthā, nor do we know anything else about her.

Info on Sela Theri:

Selā Therī. She was born in Alavi as daughter of the king: therefore
she was also called Alavikā. When she was still unmarried the Buddha
visited Alavī with Alavaka, whom he had converted, carrying his
begging bowl and robe. On that occasion Sela went with her father to
hear the Buddha preach. She became a lay disciple, but later, agitated
in mind, she joined the Order and became an arahant. After that she
lived in Sāvatthi. One day, as she was enjoying her siesta in the
Andhavana under a tree, Māra, in the guise of a stranger, approached
her and tried to tempt her. But she refuted his statements regarding
the attractions of lay life, and Māra had to retire discomfited
(S.i.134; Thig.vss.57-9).
In the time of Padumuttara Buddha Selā was born in the family of a
clansman of Hamsavatī and was given in marriage. After her husband's
death she devoted herself to the quest of good, and went from ārāma to
ārāma and vihāra to vihāra, teaching the Dhamma to followers of the
religion. One day she came to the Bodhi tree of the Buddha and sat
down there thinking, &quot;If a Buddha be peerless among men, may this tree
show the miracle of Enlightenment.&quot; Immediately the tree blazed forth,
the branches appeared golden, and the sky was all shining. Inspired by
the sight, she fell down and worshipped the tree, and sat there for
seven days. On the seventh day she performed a great feast of offering
and worship to the Buddha (ThigA.61f). Her Apadāna verses, quoted in
the Therīgāthā Commentary, are, in the Apadāna itself, attributed to a
Therī called Pañcadīpikā, and are twice repeated in these verses
(Ap.ii.519, repeated at 527f), however, she is mentioned as having
attained arahantship at the age of seven, and there is no reference to
her life as daughter of the king of Alavī.