Sorry to hear what a skag that woman was. I would be so angry, not sure how you kept it in!!
Next time go alone, kill her with kindness, if she's still a cow then say and do the bare minimum to get your packages sent. If it's still a problem you may need to go when someone else is on shift or a new post office! Don't take Tim again!
I haven't mailed too much so I don't really have postal issues, the one guy was quite stupid when I was picking up a package from my mother, he read her last name instead of mine when he asked me who it was for (not from!) I said my married last name and he's like uhh, I don't have a package, I'm like I have the slip right here, then I said my maiden name/mom's last name and he found it. Duh.
Good luck! x