Is this an appropriate behavior/custom?

my father recently got remarried to an asian women who he met over the internet. anyway, long story short, she cooks and cleans--the whole nine yards. the food was impeccable until i found out this slighty awry detail. the other day, i found out that instead of using the diswasher, she has been putting the dishes in the tub with her while she is bathing and washing them. i confronted her about it--she claims it is a custom her people have and that a symbol of an obedient woman is one who cleans the family's eating utensils with her own bathwater. also, she said they do it to save water because resources are so tight where she is from. this freaked me out and i think it is absolutely disgusting. i have refused to eat at home since, and i am sick of not being able to eat in my own home. has anyone heard of this custom? is there anything i can do about it?