Diego Seguí wrote about "Princess Mee" and "The Princess Ni":

> I do not have access to the 1924 version, but the later text as
> published in ATB relies on a pun upon the names 'Mee' and 'Shee'
> and the personal pronouns 'me' and 'she': the protagonist,
> Princess Mee, sees her own reflection on the water, and calls it
> 'Princess Shee'.
>
> Now, this pun is absent if the name is the obscure 'Ni' instead
> of 'Mee', and the whole structure of the piece may be affected,
> if it matches the latter text's.

It does not match closely. The old version is much shorter, six
four-line stanzas. What is similar is the described finery: "gossamer
shot with gold", and slippers of "fishes' mail" occur in both poems.
Like the later version, the earlier one also has an intricate
rhyme-scheme (each group of three stanzas goes: aabc cbdd effe).

> But it is striking that 'Ni' so
> much resembles the various forms of the 1st sg. personal pronoun
> in Tolkien's invented languages, examples of which can be found
> everywhere, from _nin·insta mai_ 'I am well aware' in the GL
> (PE11:52) to _nin_ 'for me' in the Namárië, and so on.
> Especially, the Early Qenya Grammar, dating from the same period
> as the poem, includes _ni-_, _nîmo_ (nom.), _ni_ / _nit_ (acc.),
> _nin_ / _nímon_ (gen.), etc. (PE14:52-3, 85-6).

The title above the poem is printed "THE PRINCESS NI", and
in the contents table it is the same, but with small capitals
following the initals. In the text, however, the name of the
princess (occurring twice, both times as a rhyme on "she") is
not _Ni_ but _Ní_.

> Is it possible that Tolkien was making a private pun in his
> poem? Note that 'Leeds University Verse' included two other
> works by Tolkien, namely 'An Evening in Tavrobel' and 'The
> Lonely Isle'; both have obvious relations with his mythos, so
> perhaps this conjecture is not too far-fetched.

In the older poem there is no mirror-motif, and the potential
pun would thus not have much point.
It is perhaps more likely that _Ní_ had originally no
intended interpretation, and that Tolkien's recognition that
it could be taken as a 1st singular gave rise to an elaboration
of the poem, eventually resulting in the substitution of _Mee_
for _Ní_.

Meneg suilaid,

Beregond

[The fact that the name of the princess in the poem is _Ní_
(with acute accent) makes me wonder -- perhaps Tolkien
_was_ making a private Elvish pun, but not the one Diego
proposed. The Gnomish Lexicon s.v. _nîr_ (2) 'woman' com-
pares the Qenya cognate _nî_, and perhaps Tolkien used
this as a convenient monosyllabic name of appropriate
meaning (if only to him!). Q _nî_ does not appear in QL as
a separate entry, though in the form _-ni_ it is well attested
there as a feminine ending: _ettani_ 'female cousin', _haruni_
'grandmother', _heruni_ 'lady', _hestani_ 'sister', _kuruni_
'witch', _veruni_ 'wife', etc. -- PHW]