This is a great thread!
I agree with everyone else, downplay your successes but don't go over the top crying "poor mouth" like you lose money on every unit. They won't believe that. I typically give a little good with the bad, never brag or rub it in when I do well, but don't pretend I am losing my butt on every unit either.
As far as the lady "running you up". That is to be expected. Expect it when you are a noobie, and expect it again later when all the regulars see you are gonna stick around and you start really competing with them.
Helpful hint* Have the capital to fight them off, know what units they like and why they are into storage auctions so you can turn the tables on them. If someone becomes a real pain, and is singleing you out to "run up", make it impossible for them to win a resoanably priced unit they want. Most people will back off once they know you can make it tough on them. Until you have enough money to play that strategy, just roll with the punches and don't overract.
The Teacher makes a great point about how much info we share about are own business on this forum. Don't know how many followers from our "neck of the woods" are lurking on this forum as guests and putting 2 & 2 together to find out who we are.