As far as I'm aware there are some very concerning things with what OP brought up that should be reported.
If you are in uniform you are prohibited from drinking. So if this FA was in uniform and even had her badge on then she is 100% in the wrong and needs to be reported. This is against Delta policies and could jeopardize other pass travelers in the future making travel harder for them. You also mentioned that she had a ticket that said "FA Jumpseat Request" on it. If so she needs to be doubly reported because she would then be breaking FAA regulations.
On the flight manifest she would be listed as a non-operating crew member (which is different from a passenger or nonrev standby employee). If anything was to ever happen to the flight she would be subject to investigation as a crew member and not a passenger which means alcohol tests and other regulations that result in response to an aircraft incident. As a crew member (even non-operating crew member) you are subject to the same policies on drinking.
The bottom line is that the only acceptable to drink if you are listed as a non-rev standby traveler.
It may not seem like a big deal or the notion of not reporting someone for being "that person" but it's a serious offense. Please don't feel like you're in the wrong if you report them, you won't be and you'll be keeping the industry safe. I know many non-rev travelers who will thank you.
Edit: I'll also add that other airline employees traveling on another airline are expected to not drink if they're in uniform.