You can't do that because it makes no sense with 'if she'd wanted to'. You can say that she should've given you some money but she didn't.

Could is used to express past possibilities or to suggest what may happen in the present or future. Should is rather used for: - recommendations: you should go see a doctor if you are feeling unwell. - to express something that is expected: the train should arrive in a minute now. - to express what you consider being right: I don't have money so my mother should give me some. - to express what you consider important to do: I should get up early this morning if I don't want to miss my train. Long time no see by the way, I hope you are doing well.

Could = past ability / polite possibility You can replace could with can only if you're talking about now or the future, not the past. Example: “I could help you tomorrow.” → “I can help you tomorrow.” Should → Can (NOT usually interchangeable) Should = advice / recommendation Can = ability or permission Example: “You should see a doctor. Replace could with can only if talking about present/future possibility. Don’t replace should with can if you want to keep the advice meaning — they express different ideas.If you want to master English grammar I would be glad to help you with your skills as an experienced teacher

Hi, you can use either or, but it will have a slightly different meaning. “Could” is used for something she possibly was able to do. “Should” is more of a recommendation for her what to do.

Hey! That's a super interesting question actually, bc it brings about the meaning of modal verbs! The sentence you wrote ''My mother could have given me some money if she'd wanted to, but she didn't'' means my mother had the ability to give me money, but she didn't want to. Whereas the sentence with should ''My mother should have given me some money if she'd wanted to, but she didn't'' is a bit more emotionally charged and can be read as ironic. The speaker is essentially saying their mother never even wanted to give them money at all, and if she did, she simply should have. You can *technically* use either one of the verbs, the sentence would be grammatically correct, but the meaning would be completely different, so at the end not the same sentence😆 You can look up meaning of modal verbs, or modal verbs meaning and read up on it! It's a super interesting topic, but it can be a bit confusing to people who just started learning. So if you already have a very good grasp on modal verbs and their basic usage, it might be worth taking a look :) Have a lovely day⭐