From women serving/gathered (exactly for what purpose unstated) outside the tabernacle to temple virgins (Mary, according to apocrypha) serving inside the second temple is a leap not justified by even the broadest reading or Scripture.
To say “...unmarried women assisting priests or making liturgical objects,..” is more than a bit vague. What were they doing? 82 virgins weaving the temple curtain twice a year? What objects? Assisting the priests in what way when that was the duty of Levites taking their turns at service?
A questionable quote from the Mishna (demonstrably unreliable) and inapplicable references to the OT do not evidence make of temple virgins and Mary being of their cult.
First, no one is making a leap to personally Mary. The frequent objection to the Protoevangelium is that there were no temple virgins in principle. We are discussing evidence that there were temple virgins as an institution. Obviously, from the existence of the temple virgins does not follow that Mary was one, and no one is claiming any different.
As to your specific question, perhaps you are not familiar with the structure of the Second Temple. The tabernacle was a substructure inside the temple; so those serving outside of the tabernacle would be inside the temple. What their service was precisely outside of the tabernacle in the Exodus 38:8 and 1 Samuel 2:22 we don't know but most rituals involve people standing at attendance, perhaps handing the priest necessary accessories, or just forming a solemn entourage. The point is that they had a set position at the door of the tabernacle.
What were they doing?
Weaving the veil of the tabernacle is specifically mentioned; as well as preparing the incense and baking "showbreads". We don't need to know what was their precise function in order to conclude that they existed.
A questionable quote from the Mishna (demonstrably unreliable) and inapplicable references to the OT
The OT references are applicable: they refer to women in some role present in the temple. The Mishnah reference may or may not be accurate even though the 82 x 10,000 threads looks like an absurd description of the veil. However, you are pretending the evidence form the Jewish tradition does not exist, whereas it is important. For example, the Babylonian Talmud Kethuboth, Pesikta Rabbatim, and 2 Baruch evidence all show that indeed these women made the veils.