I'm not sure this is MKs mother as I presume as Erwin died in Bristol, UK in 1993 that Louisa would have carried on living there but per chance whilst researching MK's parents I came across this notice of death taken from a parish newsletter from a church near Swindon, UK dated 21st October 2018...
We commend to God’s care and keeping those who have died recently especially Louisa Knopfler, Betty Darling, Alan McMeeking and Margaret Dixon. We pray for all who mourn the loss of loved ones.