The question- how do I know if a will is the final will, or if a subsequent will was written?
[...]
When the time comes, what do I do with my copy of an old will?
[...]
So the question boils down to - is there a process (besides asking her lying husband) to determine the validity of a will after a person’s death.
You will not know if your version is the latest.
The most recent valid original will presented to the probate court wins.
Valid means the person was over 18, of sound mind, not under duress, and (usually) the will was properly witnessed (in my state, that's two signatures by people who are not in the will themselves), along with some other technicalities.
Original means the actual paper the person signed, with a "wet ink" signature.
Most recent means that the court will look at the dates of all valid wills and choose the most recently dated one.
It is the probate court that will determine, not her husband. Although he may choose to challenge your will's validity, or present a will that he purports to be later than yours. The probate court will sort out any competing or contradictory claims. My understanding is that these sorts of courtroom dramas are very, very rare.
Most wills have a clause at the beginning saying that this is the last one and revokes all prior wills and codicils.
If you are named executor in the copy of the will she gave to you, and you're willing to get involved to see her wishes fulfilled, I would try to find the original copy and present it to the probate court after she passes away. The original is often kept with the attorney who wrote the will for the individual, or in a safety deposit box. If you can't find the original, you could still present your copy to the probate court - perhaps your copy is the only one that can be found.