Real-life 'moral' dilemma, should I forward the e-mail?

My “boss” sent out a spreadsheet to 8 of us that had information on it that was very obviously NOT meant for the group (financial info about the company)

She’s a horrible boss, has stabbed in the back, lied to me about my clients, and now has delayed my review AGAIN for ten months… (second time she’s done this to me, it stinks!)

I don’t know if I should forward this e-mail to HER boss or not…You can’t un-ring a bell and we all have the financial info in our hands now, but do you think that her boss SHOULD know that she did this? Do you think I’d come across as vindictive by doing this? (I’m not going to lie… I laughed to myself when I saw it and thought… how dumb!)
The other people on the e-mail are all whispers and a buzz about knowing this information also, which is driving me nuts. I’ve been here over 10 years, we’re a relatively small company and I have a loyalty to its owner and I feel terrible that she put all this info out there for all to see.

Am I a ‘rat’ if I hit that forward button?