100% legal and strange, only to the extent that you two have not discussed, but you two have only been married a year and financial planning is not something “normal” couples seem to really think about until they get pregnant.
Is this a new job or, it is open season time for most employers, is this something that just came up? Most “good” employers will offer $50k of term life as a tax-free qualified employee benefit. They may match above – I won’t go into that but she may have just made a spur of the moment decision.
In any case, some legitimate reasons, besides spur-of-the-moment, are: Wife owes Mom money (e.g., car loan, school, etc); Wife wants to take care of Mom and feels you may not feel the same sense of obligation (what is the background – is Mom practically destitute/screwed over by bad divorce, etc.); Mom is really good with financial matters (for example in our family my Father and Mother-in-Law are both exceptional to wholly reliable in financial matters); or Mom is Godmother or designated as guardian of children in the event of death(s).
At a personal level, look at this as an opportunity to move yourself and your family forward. Always know that your Wife and your Mother-in-Law will always be Mother and Child – embrace don’t fight that. And take this as an opportunity to get together with a financial planning professional and move yourselves forward in a well thought out and purposeful manner.