Well, that's a good question, and it addresses the very reason I can't define the line between the person who can't/won't go back to unbelief and the person who can go back to unbelief. I'm not convinced being born again is that line.
My wife, whom I love dearly and pray for constantly received Christ in salvation at the same time I did. We were both baptized in the Holy Spirit. She received a stunning genuine gift of the Spirit, and me, well, not sure what happened, lol, but I digress. But she, by her own admission, doesn't believe anymore. So, was she saved as evidenced by her gift, and lost her salvation? Or did she not really get saved but God gave her a legitimate gift of the Spirit anyway?
There is the account in the NT of Ananias the High Priest who prophesied in a gift of the Spirit by virtue of his calling, not by virtue of having believed in Christ. But on the other hand, Paul does talk about the gifts being distributed to the body of Christ, meaning of course, saved people. So I don't know what exactly to make of the people in Matthew 7 operating in legitimate gifts of the Spirit, yet not belonging to Christ. Perhaps they are working false miracles. I don't know. I honestly don't think them being believers in Christ and them being rejected by Christ is an option. One thing's for sure though; they are guilty of not living in obedience to Christ. That to me tells me they are not real believers. And so it's just a question of whether or not their gifts are for real. Are they? I don't know.
Taken in a scientific-like perspective, where a scientist must consider all data and include it in the equation in order to come to an accurate, truthful, real-world conclusion about the given experiment or topic of study, it sounds to me more like you are choosing to ignore
known data and not include it in the equation than not understanding all of the data as it exists, or is presented.
Here's the data you admit to having:
A. The Bible shows, in multiple ways, that there are some who are doing things that can only be done by believers
who are ultimately rejected.
B. The Bible tells us, through Jesus' own words, that people are not
capable of doing these things unless they are believers; unless they have the Power of God working in and through them via the Holy Spirit.
C. The Bible clearly makes the case that these are believers who are doing these things.
Here are your pre-existing beliefs:
A. You believe in OSAS; nobody can ever lose their salvation.
B. You believe your wife has completely lost all her faith (belief).
Therefore, rather than believing the data you clearly see provided in Scripture, you are making a decision (consciously/unconsciously) to ignore what the Bible says and refuse to believe that a believer can be rejected by God.
In that case, it matters not that your wife lost her faith because there is evidence in Scripture that even those
with faith can be rejected for living a life of sin; that is a life outside of the Commandments of God -
even believers.
Again, even the demons believe,
more so than any human ever could, and you can rest assured they will not be in heaven.
James 2:19