Lost keys are very common on our site so your mom should not feel upset about this if she does. The answer given by all of our experts first is to contact Sentry directly as they will be able to send a key out to you and your mom. The issue though is that is takes a short amount of time to do so. The instructions to follow can be found here in this link I have provided:
You might wish to try this method as many have tried this and it has worked for them:
Other than this, calling a locksmith tomorrow will be your best bet in order to open the safe without damaging it.
I hope that the suggestions listed were found helpful. If you could please take a quick moment to rate my assistance so that I can receive credit for helping you today.