The movie also specifies she taught Coco when she was already grown. Have you ever worked with shoes, anon? It is a shitload of work. And Imelda had to do that shit by herself at first. Ponte en sus zapatos.
And there’s jackshit that makes your point valid. There’s no evidence, all you got to support yourself are literal headcanons, meanwhile you have statements that Imelda was the one who worked to sustain and that Hector “abandoned” them. Hence, there’s no reason to believe he supported them financially.
And of course Imelda forgave him at the end, she realized it would’ve been different if he wasn’t murdered, he wanted to change, he helped Miguel, he proved his worth and Imelda never got over him. The fact she resented him so much is just a way to channel her feelings because she still loved someone who, in her eyes, hurt her and her family. You just have to pay attention to the scene after she and pepita rescue Miguel and Hector. She’a full of hatred for him, has rejected him many times in the past because she’s still hurting but once they got over that, and could actually work and just be together after explaining why is that he couldn’t come back to his family it was obvious her feelings would blossom again.