Legal Question in Wills and Trusts in Missouri

If the account had right of survivorship, then your sister may have no legal claim to the funds, and you do not have to submit it to probate. Unless the account was one where you were holding money in trust for your mother, you are not precluded from removing all your money after your mother's death.

The question of what is "your" money seems more a moral than legal question giving what was described above. Legally it may all be your snow that your co-accoutn holder has passed. but, since it is yrou mother sister that wer are talking about, you might ask yourself how your mother considered the money in that account.

Good luck