I don't like coffee. I do have a coffee maker for guests who do. The Professor doesn't drink it either, but he knows how to make it -- I guess. I generally ask the most ardent coffee lover guest around to do the honors. That way, we can be pretty sure it turns out well. I think your MIL, who apparently doesn't drink coffee either, might have adopted this tactic profitably. She also might have laughed and said, "oh, you make it, then" which would give you Command of the Coffee Maker. Whether or not DH was rude depends on how his family works. If she would say to him (or you), "no, no, you're doing that sauce all wrong. That's going to be awful! Here, let me show you," it was probably OK, or close to it. If MIL would say that to him, but not you, I think both of you were fine. As someone said, family culture. With maybe a touch of brat and disrespect on his part. He could have been much, much nicer.
My mother will instruct anybody, anywhere, anytime on the correct way to make tea. She views this as a mission. She is pretty tactful about it, considering how strongly she feels about it, and usually phrases it as "May I make Elsewherian tea for you?" She brings her own, despises bags, and won't touch tea anywhere if it is not prepared according to her picky specifications. She asks for water or something else easily and obviously available when only terrible tea is likely to be available and she can't offer to make it properly. When I have the option, I use her approach as a preemptive strike. When presented with a cup of the undrinkable, and it would be unkind (etiquette is often about kindness) to dump or ignore it, I will take a sip or two, and play with it until I can say, "Oh, dear, this has gone cold," and ask for something else, usually water, or offer make Real, Elsewherian, tea, which I happen to conveniently have with me, if that is possible. FWIW
I think you would be fine picking up whatever kind of coffee you like and presenting it her, saying you think this is better for her machine, and may you make a pot that perhaps she would like to taste? And, since she is hosting both you, take her out to dinner or buy the ingredients and cook for her.