Stop being selfish and leave the poor girl alone! you can't MAKE her want to quilt! or generally be craft for that matter. Be happy that if the time comes that you son needs a button sewn on something she can do it. Many women these days CAN'T and WON'T! Go find youself someone else to quilt with and leave the poor DIL alone.
My husbands grandmother (she raised him so refer to her as my HatefulMIL) is a shopper she loves to buy clothing and just junk in general. I am not this way. I don't care to have crap all over my walls and fancy rugs on my floors. Well this woman tried pushing and pushing her ways on me. I can NOT stand the woman now and any time she buys crap for the house and sends it here I throw it out. Even if it were something that I would have liked years ago before she pushed her ways on me......
So my advice STOP. before she takes it personal and stops likeing not only your hobby but also YOU! You wouldn't want to make them a beautiful quilt and her be so turned off that she trashes it!