Did I overreact or is my question valid?

I had given my mom some money to store for a while and when she gave it back it was $71 short. I told her and she made a big scene. Tonight I asked her again because she began making up a bunch of stupid excuses and lied that she had given me $40 in one occasion that was total bullshit, so I asked her again how is it possible that I'm missing $71 if I am 100% sure that I only took out $40 and she started saying "don't you eat? Don't you use soap" bla bla bla. I told her, but that has nothing to do with my question, why are you avoiding it? Then she began screaming that "are you accusing us? Whatch your words!" And being such a drama queen and making a scene that I thought foam was coming out of her mouth, it really pissed me off. Because I think it was a really valid question, how was it possible that $71 went missing? The only explanation is that somebody took them, and I can't believe my own family would do something like that to me.
Did I overreact or is my question valid?
Post Opinion