Need help deciding between a 2012 Prius C, a 2012 Prius, or 2003 Corolla with failing transmission

Hello! Attempting to wrap my head around these options I came across this forum. I'm currently driving a 2003 Corolla that I inherited from my grandmother when she passed away in 2017. It had 78k miles on it and major drive-train issues that I got repaired when I got it (she lived near the ocean and there was corrosion damage to it), and I suspect that she did not stay on top of the regular maintenance during her final years. That being said, I've been using it for the past 5 years, keeping regular maintenance, and periodically having to replace/repair several engine components (sorry, I live in Puerto Rico and I don't know what the components are called in English- here they call them "bobinas" and they are somehow related to the spark plugs). Most recently, around the 100k mile mark a couple of months ago, the transmission has begun slipping, and I'm trying to decide whether it's worth repairing (I got a quote for $1350 to get it repaired, with a 1 year warranty).

I would get a newer corolla, but I'm having hard time finding one withing my budget of $10-13k. I test-drove a 2012 Prius C at a used-car dealer today with 47k miles on sale for $10k that flashed a warning about the hybrid system, and after scanning the computer got code P3020. I called a hybrid-specialized shop that informed me that code is for a battery block, but that they are not worth repairing and that the battery should be replaced, which will cost about $3,000. The same shop is offering to sell me a 2012 Prius for $12500 that has 134k miles on it, with a 1 year service warranty with them and a recently replaced hybrid battery (2 years ago).

Ideally (although granted, this may very well be wishful thinking), I will be driving this car for the next 10 years or so. Based on my Corolla usage, I seem to average about 5k miles per year. So, these seem to be my options:

1. Offer $7000 for the 47k mile prius C and spend another $3000 to get the battery replaced (unlikely they will accept, but maybe worth a shot, although I'm not enamored of the low-visibility out the rear window in this car). There is also a battery shortage which may limit my ability to get it repaired soon.
   
2. Go for the $12,500 134k mile 2012 Prius with a 1-year warranty directly from a specialized hybrid repair shop
3. Get the transmission replaced on my 2003 103k mile Corolla, while accepting that it may continue presenting more problems down the road, while I wait for a newer Corolla within my budget to appear on the market.

Any advice on this will be greatly appreciated!