I've never understood this mentality. I just took orders and delivered them. All of my drivers would lose their shit about which orders were tipping what, so I'd just grab the contentious ones and get them done. I can't tell you how many of those turned into some of my best customers and also some of my wildest experiences. Also, a few people that were expecting to be treated like shit for not pre-tipping would then call in to thank my manager for my service and attitude despite it, I remember one was a single mother who looked, traumatized, when she opened the door. We were allowed to comp a certain number of orders a night so I did that for her and she just started crying. I never forget that one. So not worrying about it literally paid for itself with several raises and a promotion. Sure, there were dickbags who would stiff you but it all came out in the end. So, my advice is to just do your job and it will work out. If people see that they can rely on you to get it done right every time then they are far more likely to tip better on the next one, so just treat every delivery as one you'll be tipped for later. If you're not getting paid, then get a different job. ,
I did get a few unconventional tips too. One guy would just give me a beer and then the option to drink it real quick with him (stupid, I know, but I don't drink anymore and luckily I never killed anyone). There was a group of Canadian travelers that would give me an entire case when they came through. And also an entire bag packed tight with very potent weed, in exchange for my delivery bag. I have no idea why they wanted it so bad, but while considering it they gave me a shot of something and then they flashed me. I wasn't actually considering what to do. I was already really stoned at the time and was struggling to get the words out that I would accept. But the unexpected tits sobered me up instantly and I handed the bag over. My buddy realized that I was trashed when I got in that night so he put me on dishes for cover. When it was discovered, I blamed the missing bag on a dickweed that had recently been fired and they asked no more questions. An older guy gave me a pirate Lego set, it was a little island with a palm tree and a treasure chest. And a delivery that was technically outside our area but missed by the computer turned out to be a ring holding and famously nicknamed NFL player. His driveway was a very long previously unmaintained road that had once intersected a road in our service area. But that was blocked off and access was from the other side of an enormous housing development of mansions. Never knew that was a thing. There were a lot of pools. And lights. That's all I remember though.
I'm sure it's been mentioned, but maybe she could benefit from a sponsor peer? Our puppy was a swimming sponsor for 12 years. Dogs who were terrified of water would come to the pool with our dog and would usually be broken of the fear at least in shallow water within the first 30 minutes. After 3 swims they were almost always on their own after that without any issues. There was only one dog that never swam and that was of a possibly abusive owner.
So maybe there is a puppy friend that she is fond of that can make her feel at ease? Hope it helps, good luck!