There's a difference between a "non-traditional" serve and a sneak serve. Nothing wrong with serving any way that's legal, but for a server to appear as if she is not ready to serve, then suddenly push the ball over the net (as Lendl did to McEnroe famously)... that's BUSH.
So, which way did your old lady do it?
I think this sort of thing is bush, but for a different reason. I mean, if the receiver is ready, he's ready. He can't become unready absent outside interference.
Still . . .
I think there is a subtle reason why folks consider underhand serving bush but are willing to tolerate or even applaud other "surprise" shots like droppers or lobs or head fakes.
The Code seems to suggest that players are supposed to start each point off in a certain way. Server must wait for receiver to be ready, after which receiver has to stay ready. Server cannot move around. Server has to serve within a certain defined space. Server cannot suddenly vary his tempo (quick serving). Server is held to a pretty rigid standard, if you think about it.
Receiver, on the other hand, gets a bit of freedom. He can become unready if there is outside interference. He can feint with the body. Receiver's partner can get in on the act and stand in the middle of the box if she wants.
The Code's approach to the moments before the serve is struck is somewhere between "neutral" and "favoring the receiver."
But once the point starts, all bets are off. Players can move however they want, and they can use any trick shot or surprise tactic that they want so long as the intent isn't solely to distract. The Code no longer cares about a level playing field once the point starts, and restrictions apply to both sides equally.
In that context, we have the underhand serve. In practice, the underhand serve is *always* done to surprise the receiver. Servers do everything they can to hide their intentions and mimic other pre-serve behaviors, as in AngleQueen's case.
It is the Server's deliberate trickery *before the point starts* that is bothersome, IMHO. The Code seems to want to tie the server's hands and keep the pre-point shenanigans to a minimum, and here we have a server who has found a way to "surprise" the receiver anyway.
So yes, it's legal. It's also bush league. People can be bush if they want. I would never say a word about it were I in AngleQueen's shoes. But yes, I would secretly think it was bush.
Maybe we can come up with a name for those players. We have declared that some players are"Pushers." Perhaps folks who use the underhand serve to surprise their opponents are "Bushers."