Also I look at a covenant like a will. If someone had written six wills only the last will would be valid because that last will canceled out all 5 of those previous wills. Is this wrong thinking when looking at the different covenants? I would like your view.If a covenant is designed to replace an earlier covenant, this woman is correct. This is the case with wills, as is the case with the "old covenant" vs the "new covenant". (The "old covenant" is defined in Jeremiah 31 as the Mosaic Law, given at Mt. Sinai, but has nothing to do with earlier covenants, such as the Noahic covenant, and/or later, different covenants, such as the one God made with David to keep a descendant of David's on the throne forever - Jeremiah 33:20-22 - a covenant fulfilled in Jesus, a descendant of David.)
But just because you enter into a new covenant, that does not necessarily mean any previous covenants you had become null. For example, if you get a new credit card and run up a balance, you now have a new covenant to pay that bill; this does not in any way nullify other credit card balances you had previously; you are still bound by those earlier covenants.
God made a covenant with all of humanity in the Adamic covenant (be fruitful; multiply; steward the earth; live a vegetarian lifestyle; etc).
He made another covenant with all of humanity in the Edenic covenant. The new conditions of the Edenic covenant (toil; labor; pain in childbirth; death; a promised messiah) did not nullify the conditions of the Adamic covenant (be fruitful; multiply; steward the earth; etc).
He made another covenant with all the earth and all the animals and with all of humanity in the Noahic covenant (no more global flooding; seasons; rainbows; capital punishment for murderers; skittishness of humans in animals; etc). This covenant did not nullify the conditions of the earlier two covenants: humanity was still to multiply and take care of the earth, and was still subject to hard work and pain and death, and still had the right to look forward to a messiah. Note however that this new covenant did include one condition that was the same as in a previous covenant: "be fruitful and multiply". It also gave a new permission which over-rides one of the stipulations of an earlier covenant: we now could eat meat. This might be analogous to a house-owner entering into a contract with you to rent to you a house with a stipulation that you could only paint the house green, and then sometime later writing up a new contract with you for renting to you a car also, and which also has a clause within it giving you the right to paint your house red in addition to the green of the first contract.
He made another covenant with Abram, and this covenant is actually referred to in Gal 3:8 as "the gospel". This covenant was originally only for Abram's descendants (a subset of humanity), but hinted at including all of humanity somewhere down the road. Paul finishes up Galatians chapter 3 by claiming that all Christians, even if they're not physical descendants of Abram, are spiritual descendants of him, and have thus inherited this covenant. This covenant did not nullify the conditions of the earlier covenants: humanity was still to multiply and take care of the earth, and was still subject to hard work and pain and death, and still had the right to look forward to a messiah, and still enjoyed freedom from global floods, and still was comforted by the rainbow's promise, and still had a hard time catching animals because of their instinctual skittishness of humans.
Then he made a covenant only with the Israelites (a subset of Abram's descendants)
Then he made a covenant with King David (a subset of the Israelites), that there would always be a descendant of David on the throne. This covenant is still in effect, with the role of throne-sitter being held by Jesus. This covenant did not nullify the conditions of any of the earlier covenants.
Then he made a new covenant with all of humanity, with Jesus as the mediator. This covenant did not nullify most of the earlier covenants, but it did nullify one: the Mosaic Covenant, the one which had been expressly singled out by Jeremiah as being earmarked for replacement. But notice that even at that, it's not so much a replacement as a spiritualizing: rather than the law being written down in regulations on a stone tablet, it's written down in family relationships in our hearts.
Just like a teenager might need a written rule to mow the lawn every week, a grown adult will take it upon himself to make sure his older parents' lawn gets mown, because that "rule" is now in his heart, not on the fridge-side "to do" list.
So hopefully you can see that some covenants do replace earlier covenants, such as wills, whereas some covenants do not replace earlier covenants.