Women appear in ministry functions and even recognized roles in both the Old Testament and New Testament (source). I believe, that the earliest mandate for women in ministry is that given right at the beginning - the command given to co-steward the Earth (in conjunction with men):
26 Then God said, “Let us make man in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth.”
27 So God created man in his own image,
in the image of God he created him;
male and female he created them.
28 And God blessed them. And God said to them, “Be fruitful and multiply and fill the earth and subdue it, and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth.” - Genesis 1:26-28 ESV (emphasis added)
A consequence of the fall, was that the deception of Eve resulted in a curse on her to be under the rule of her husband in a way that worked against her own desire for him (a subjection - cf. Genesis 3:16). It is true, that Adam was made first and there is a sense that Eve was made 'for him'; but it is also true that a male/female partnership with both being co-image-bearers was in God's heart as evidenced in the passage quoted above - the curse bought a sense of dominance as opposed to 'first among equals'. This curse was unfortunately transmitted to subsequent generations and indeed had a highly deleterious effect on women's ability to minister according to their original dominion (co-)mandate and remained in effect until it was broken at Calvary*. The ministries of Deborah and Huldah in the OT were exceptions that gave a glimmer of hope that God's grace was sufficient to overcome the curse by those who put their trust in Him.
The most significant verse on the matter in the OT is not the examples of the two women mentioned however, but:
28 “And it shall come to pass afterward,
that I will pour out my Spirit on all flesh;
your sons and your daughters shall prophesy,
your old men shall dream dreams,
and your young men shall see visions.
29 Even on the male and female servants
in those days I will pour out my Spirit. - Joel 2:28-29 ESV
Which of course received initial fulfilment on the day of Pentecost but remains an aspect of the 'now but not yet'-ness of the Kingdom of God - until the cloudbursts of the latter rain, it will be those who press in to the Kingdom that will lay hold of this truth, while others will fail to grasp it.
I believe that it is in this over-all context, that a deeper meaning than just implied by the immediate context can be seen in the oft-quoted (by egalitarians) Galatians 3:28 -
There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus.
In Christ, women are liberated from the curse of domination to become all they can be in him - including walking in a life of good works prepared for them (cf. Ephesians 2:10) for:
Whoever is a believer in Christ is a new creation. The old way of living has disappeared. A new way of living has come into existence. - 2 Corinthians 5:17 GW
Many will still say, but what about 1 Corinthians 14:33-35 and 1 Timothy 2:11-12? I would answer that these passages must be examined very carefully in light of the context of what the whole of scripture tells us - they represent examples of what 2 Peter 3:15-16 is talking about -
15 And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, 16 as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures. - ESV (emphasis added)
For those who are interested in further study of these matters, I would direct them here,here or here.
*In an analagous way to how scripture teaches us of other Calvary associated benefits (e.g. healing), I believe that this benefit must be appropriated by faith in God's grace.