However she has not declared in her country that she is no longer a tax resident there.
There is your problem and your solution. Just get it over with and complete this process. Then when you return to Latin America become a tax resident again.
If her Binance account is connected to her Latin American bank card, am I right that only Latin American tax agencies will be informed about her crypto assets/ transactions on Binance?
Ignore all the posters that may say otherwise, they don't understand how deep the KYC network is. Despite how you used Binance for her, the KYC network knows who her husband is and where she is living now in most cases. Therefore, you are at risk of the other tax agency being informed. The risk is not high, but it is possible. You need to think also more generally. It is not that someone is going after you specifically, but there may be a general ask for information by the EU or a specific country to Binance and it will get you too.