Cloris Leqchman

I see that Cloris is going to be in this film and was wondering if she is going to play Cameron's characters mother. If so this worries me as she is 85 years old and even with the biggest stretch of my imagination I cannot see her as her mother. Cloris is 85 this means that for the last 40 years she most likely could not have mothered a child. This casting of old mothers has always bothered me, there are many films where mothers are cast and common sense would tell you that the actress is way too old. Especially period films like Valmont where the young girl is 15 and has a mother who looks 50 and the mother is marrying off the 15 yearold, you would presume the mother would have been only 16/18 when she had her and she should only be in her 30's.
Hopefully Cloris is the grandmother.