She needs to see you in person.
It could be linen, but people get fooled on that one as much as they do when they think they have silk rugs when they are instead rayon.
She also needs to have a discussion about dry cleaning. Yeah, its not the way to go 99.9999999999999999% of the time, but her question might mean that she'll look for trouble if you don't dry clean it. If she feels like you just don't want to do it, and if there is the smallest of post cleaning issues (slight texture change, some puckering of the cushions from minor shrinkage, a little "overwhitening" in the areas you clean more aggressively, anything....) she might make a big deal over it. So don't rush through that conversation with her.
I agree with the above comments regarding protector. White natural fiber fabrics should be protected.