Erika
This is Kawaguchi Hidetoshi. This is a humble answer to the question.
The content is slightly different from that of this consultation, but I have answered the question below by listing “My Parent's Love Story.”
Question “I'm taking care of my parents in a situation where I have no choice but to separate from my husband”
http://hasunoha.jp/questions/125
Question “How to deal with my real mother”
http://hasunoha.jp/questions/146
Although the false sutra theory of the founding of China is dominant in the “Parental Grace Song,” it contains good content to encourage the practice of Buddhism in order to reward that kindness by listing ten items of kindness from parents.
http://ja.wikipedia.org/wiki/仏説父母恩重難報経
Quotations from the section “Reward the Seekers”...
“If parents are stubborn, don't try to respect the Three Treasures, hurt people without compassion, do injustices and steal things, have no sense of decency and are lustful, mock people without trust, and indulge in alcohol by making them intellectually difficult, then children should be just harshly reprimanded and made to be prepared for such behavior.” Yes, there it is. This is important even if you are not a seeker.
It is a bad act against a mother to commit stealing, even if it is between relatives, so I know that it is necessary to discourage them in order not to cause them to do any more bad acts and not cause them to accumulate bad karma.
If this eventually leads to theft of money or goods from other people, it will become even more difficult, so I think it is necessary to strongly apologize after consulting with everyone in the family as much as possible.
Also, it will be necessary to find out the cause of why they steal. If you are in trouble with money, try to make up for it with clear balance accounting with the cooperation of your family. If there is a high possibility that the cause is a mental illness, it may be necessary to consult with related institutions along with the cooperation of the family (reduction of stress/dissatisfaction, etc.), and in some cases go to psychosomatic medicine.
Anyway, stealing is a crime and misconduct, so I think it would be good for Erika to aim for a solution after investigating what the cause is along with being careful not to let her mother steal it.
Kawaguchi Hidetoshi Gassho