It's disrespectful, yes, but not offensive. Thing is, she set out to be disrespectful, didn't she - wasn't that the whole point of the exercise? It's an organization that deserves no respect and the so-called Memorial Observance by JW's is a sham, and is in itself very disrespectful to Christians and to what Jesus originally intended, it seems.
That said, I found it pretty tacky but I'm sure I don't share her sense of humor. It wasn't funny at all; but not offensive. I don't know if Brenda threw in the low class gum chewing as an extra touch or if it's just something she naturally does.
I don't believe the stunt will prove to be effective in any way, but who can tell. Seems the wrong way to go about it to me. If she just needed to get it out of her system after being treated derisively herself within the Org, then maybe having done it will help her in some way, and that would be fine and good I expect.