Not knowing how old your sister's MIL is, I am 59 and my friends and I have gotten to the point that we really don't need anything, so being taken out for a meal is wonderful. Or if you have a local place that has gift cards, that is nice. And flowers are great too. Would she mind if you watched her do it? Then you can get an idea what all is entailed and maybe learn to do it. A friend comes over and in the beginning she was having me do the embroidery on my machine - now I have her do it. While she embroiders I do something else, like piece or quilt or hand sew. I love having the company and sharing the love of the hobby is great. Also, it is great to see it all come together. My friend is so my more creative than I am.
Just make sure you bring over all the thread you need - a brand that she likes to use.