I need some serious help, please.?

It's good that you tried talking to your mom. If she gets angry when talking to you, tell her you'd like to speak to her without yelling because yelling gets people nowhere. I'd say just do what she says so that she can't yell at you about something that you already took care of, like cleaning up the crumbs. Your mom is probably just a little worried about mess in the house right now since your cousin is a guest, and I know my parents get stressed out when there is mess from guests. So just obey your mom right now, show a cool attitude toward her (since an angry answer can make other people angry and thus blow up situations), and let your mom have some space to cool down and blow off steam. You're doing all you can right now. Take care.