Dual citizenship A-B (non US), Passport expiring

I apologize for the seemingly contrived question, but this is actually my current situation, or rather, my mother's, and I am at a loss on what exactly she should do.

She is a Citizen of Venezuela and Colombia, and holds both passports.

She has a valid, current U.S. B-1 Visa in a long-expired Venezuelan passport. She also has a currently valid Venezuelan passport that expires in October. We are currently trying to get a renewal but due to the mess the country's in, she may not be able to get it before going to Colombia in a few weeks.

She has her Colombian valid passport with a much longer expiration date.

She wants to come visit me in Germany, and has a ticket flying out of Colombia with a stopover in the U.S.

Here the timeline and questions/confirmations:

1) Flying out of Colombia, she must show her Colombian passport, as a citizen.

2) Stopover in the U.S. The U.S. Visa is on the old Venezuelan passport, so she must show that one. She must also show the newer, valid Venezuelan passport that expires in October. Q.: Will the upcoming near expiration date be a problem for the stopover?

3) Entry into Schengen. Both Venezuela and Colombia have the same privileges when entering Schengen (no need to apply for visa beforehand), so Q: I assume it would then be ok to just show the Colombian passport to gain entry and get the stamp.

Bigger problem: the flight back, in January. By then, she would have 2 expired Venezuelan passports, and her Colombian current one.

4) Leaving Schengen, show the Colombian one she used to gain entry.

5) Stopover in the U.S. Now the Visa is on a different country's passport (Venezuela) as her ONLY valid passport at the moment (Colombia). Should she instead get an ESTA with her Colombian passport? Should she show them both? Will the ICE/TSA agent even understand what the heck is going on?

This last question is the crux of my post. Thank you for bearing with it for this long.

I would really appreciate any guidance/advice you can give me, even if just to point me in the right direction.

Thanks.

Edit after answers:

Thank you all. First of all, I apologize for using the wrong agency. When I said ICE/TSA I meant (and should have said) USCBP.

I got in touch with the U.S. Embassy in Venezuela, they told me to get in touch with USCBP. I tried looking in their website and found nothing, and I tried their customer service line and was absolutely unable to navigate out of their dumb menu answering system.

I did not think about the fact that the airline was the one to decide in the first place whether she even boards the plane headed for the U.S. stopover. If the airline allowed it, I suppose I couldn't really understand what the CBP agent in the stopover airport (Newark, in case it matters) could do. I mean, my mother would already be there, what will they do, deport her? She already has an outgoing flight to the country they would deport her to. That sounded just crazy to me.

I suppose the only other option would be to have her apply in Bogota for a second US visa, on her Colombian passport, but I thought it would be illegal/not allowed for one person to have two visas just because they have two nationalities.

I also misspoke when I mentioned ESTA. Neither Venezuela nor Colombia are in the VWP, so ESTA is out of the question.

Thank you for your answers so far, and if anyone has some brilliant idea of what to do or even where to call to find out, I'll be even more grateful.