I must confess I was a bit worried since we hadn't heard from you in so long.

The pawing thing is probably separation anxiety related but I suspect that it's tied in with the anxiety she feels when she thinks that it might be feeding time or treat time.
The reason that I seldom use feed or treats for motivators or rewards is because when you introduce feed into the equasion, most horses instinctively flip immediately to the reactionary side of the brain and it builds anxiety which in turn builds energy and excitement and horses are incapable of thought when they're excited.
You've probably stopped with the treats but that doesn't mean that she don't revert to old habits every time she sees you/humans coming.
Just like any other habit with a horse, both the good and the bad, they die hard. That's why we work so hard to reinforce good habits and never let a bad habit get started.

There are a few things you could do to discourage it if it continues to be a problem. For one, you could take the time to make her feel uncomfortable some how every time she does it. It doesn't have to be any real discomfort, any amount will do over time. There are lots of ways of doing that but what you don't want to do is go over and soothe her anxiety by comforting her. That seems the thing to do but what it does is gives her relief and she continues to associate your presence with relief, which is usually a good thing, and something we strive for, but in this case, it's working against her/you by rewarding and reinforcing the anxiety she's feeling and causes it to get worse.
Another thing you could do is make sure that she don't get fed every time you/some human comes around. And definitely don't be giving her any treats.

We tend to confuse excitement/anxiety with happiness/appreciation when we give a treat to a horse but what we're really doing is creating undesirable instinctive behavior that progressively worsens. I might even go so far as to pick up a few pebbles before I went out there and toss them at her til she stops pawing before I approach close enough for her to smell me (cuz I don't really want her associating me with discomfort which she will if she can smell you). You'd think that would make her dislike you but the truth is... horses are stupid and she won't even realize that it's you tossing them... she'll think that the pawing gods are angry with her... not really because horses don't posess the ability to reason, but if a pebble should fall from the heavens and land on her every time she starts pawing, she'll soon associate pawing with discomfort and without even thinking about it, she'll instictively stop that stuff. Even when she sees your arm moving, she still won't put 2 and 2 together so it won't count against you.

She may even quckly learn that when your arm moves, something taps her but even then.... She won't realize that you're actually causing it. Like the Beverly Hillbillies never understood why every time they heard that mysterious bell music, someone soon showed up at the door. After a while, just the movement of your arm might be enough discomfort to discourage that, even if you should miss with the pebble.

Of course I'd have to see it a couple times to determine exactly what causes it to be absolutely sure, but whatever the case, she needs to stop that for all the reasons you listed, plus, that kind of insecurity can show up in other places like performance or manners and it can become a safety issue, amongst other things, and we want her calm and confident, not anxious and insecure.
If you ARE still giving her treats... You should stop for a while. Then, never, under any circumstances, give her a treat if she's expecting it or anticipating it or even hoping for it. The only time you should ever give a horse a treat is when it's totally unexpected, which usually means, very seldom.

A good rubbing/sratching, done right so it actually feels good to the horse instead of just irritating her, will gain you more favor with her than any treat ever could anyway because she learns to associate you with feeling good and relaxation... Relaxation is the first thing we want them to feel when they see us... not anxiety.. whatever the source of that anxiety may be.