Sorry, but I’m unsure which Patrick McDOWALL you refer to and I don't know who Margaret was. If you are able to access a copy of Nisbet's "A System of Heraldry", volume 2 is supposed to have an appendix giving the Freuch line of McDOWALL to 1721, as claimed by the then Patrick McDOWALL of Freuch. Maybe she gets a mention. Burke's Landed Gentry may also be worth a try, but whatever you find will be questionable. There were lots of squabbles over land, religion, and allegiance to kings and political leaders. These led to lots of claims and counterclaims regarding ancestry, so it is hard to know what is true.