Tl;dr: No, I don't think there's consensus about how the Hebrew "זַרְעָ֑הּ ה֚וּא" should be translated, but the pronoun "she" doesn't seem to be justified in my view and receives little scholarly support.
I found 2 good articles on Genesis 3:15 by OT scholars (no paywall):
here and here. A non-journal article describing the Catholic position that I think is representative is here.
I'm very partial to the argument made by Collins (first link) that the noun "זֶרַע" describes an individual rather than Eve's posterity in general because essentially everywhere else where the Hebrew has "זֶרַע" as the antecedent of a singular pronoun e.g. "זַרְעָ֑הּ ה֚וּא" it refers to a single individual (for another example he gives 2 Samuel 7:12-13:
"וַהֲקִימֹתִ֤י אֶֽת־זַרְעֲךָ֙ אַחֲרֶ֔יךָ אֲשֶׁ֥ר יֵצֵ֖א מִמֵּעֶ֑יךָ וַהֲכִינֹתִ֖י אֶת־מַמְלַכְתּֽוֹ׃
ה֥וּא יִבְנֶה־בַּ֖יִת לִשְׁמִ֑י וְכֹנַנְתִּ֛י אֶת־כִּסֵּ֥א מַמְלַכְתּ֖וֹ עַד־עוֹלָֽם׃"
"...I will raise up your offspring to succeed you, your own flesh and blood, and I will establish his kingdom. 13 He is the one who will build a house for my Name, and I will establish the throne of his kingdom forever." (NIV) Here "זַרְעֲךָ֙" ("your seed/offspring") is a prophesy about a specific person (Solomon) and therefore is the antecedent for the pronoun "ה֥וּא" at the beginning of v.13 which is singular.
As an example of general "posterity" he gives Genesis 17:9:
"אַתָּ֛ה וְזַרְעֲךָ֥ אַֽחֲרֶ֖יךָ לְדֹרֹתָֽם" ("you and your descendants after you for the generations to come"). The key here, I think, is that the suffix "יךָ-" on "אַֽחֲרֶ֖" ("after") is a plural masculine suffix indicating that "זַרְעֲךָ֥" is to be taken as plural.
Collins does note that much scholarship about Genesis 3:15 treats it as referring to a general or collective posterity, however, and you can examine the sources he cites for yourself.
As for the gender of the pronoun "ה֚וּא", the scholarly articles are dismissive of translating it as "she." Collins says:
That is to say, the word zera‘(‘seed’) is taken as a collective,
and the pronoun hû’ is masculine singular in order to match
its antecedent (za‘āh, ‘her seed’), and is better rendered ‘it’
or even ‘they’ (so too the suffix on těšûpennû, ‘you will bruise him/
it/them’). Authors who find a Messianic promise in this verse
do not usually dissent from this grammatical analysis. They
tend to see the Messiah as the representative or crystallisation of the woman’s seed/posterity.
So he doesn't even mention "she." The second article does, but treats it as a footnote:
The fact is also well known that the LXX chose to render the Hebrew pronoun hu' with autos, making it a masculine, whereas the Hebrew does not demand anything more than a neuter. The Vulgate, on the other hand, rendered this same pronoun with the feminine ipsa, thus giving support to a mariological understanding.
In its longer discussion of "ה֚וּא" the second article says the main contest is between "he" and "it":
Translation Problem Two: How to render the pronoun hu'.-- In the Hebrew text this pronoun refers back to zerac, which is a masculine word. Thus the masculine hu' could simply be explained in this sense. Since in English the word "seed" is neuter one could defend the choice of "it" as a translation for hu'. This is the way the King James Version rendered it, though both ASV and RSV use "he." The Dutch New Version retains "it." This reflects the ambiguity of the original and, in a certain sense therefore, might be called a good translation.
However, the rendering "he" has also some very ancient and venerable support. The Septuagint chose that word (Greek: autos). This choice is all the more remarkable since the Greek, in distinction from the Hebrew, has a choice of masculine, feminine, and neuter. The Greek word for "seed" (sperma) being a neuter, the Septuagint could have followed this up with a neuter (auto). Apparently it felt the personal reference at this point to be strong enough to choose autos instead. And, indeed, something of the personal next to the collective does play a role in this passage.
Finally, even the Catholic article concedes that the rendering "she" is probably an error even if it expresses a defensible idea:
Christians have recognized since the first century that the woman and her seed of Genesis 3:15 do not simply stand for Eve and one of her righteous sons, such as Abel or Seth. They prophetically foreshadow Mary and Jesus. The first half of the verse (speaking of the enmity between the serpent and the woman) has been applied to Mary, and so the second half (speaking of the crushed head and heel striking) also has been applied to Mary.
Though the variant that uses “she” and “her” probably came from a copyist’s error, the idea it expresses is true. There is a sense in which Mary crushed the serpent’s head and in which she was struck at by the serpent. She didn’t do these things directly, but indirectly, through her Son. It was Jesus who directly crushed the serpent’s head from the cross and Jesus whom the serpent directly struck on the cross. Yet Mary cooperated in these events.
So in summary, it seems that "she" is probably not the best translation of "ה֚וּא" in Genesis 3:15. In contrast with Revelation Lad's answer, I didn't find anyone who interpreted the pronoun as actually referring to Eve. It seems to most likely be a copyist's error, as you noted, and probably intends to refer to Mary.
Disclaimer: I'm just starting my study of Biblical Hebrew, so while I'm trying to confirm this answer with authoritative sources I have little experience myself. I used the Polyglot Bible with Strong's lexicon in preparing this answer. For English translations of the Hebrew text I used the NIV.