Scam? No way! She's the salesperson and it's a tactic - and a pretty darned good one sometimes.
Some common and some sophisticated diamond scams
If you have shortlisted your acceptable diamond sellers and qualified them as ethical, then you only need to be wary of sales tactics.
A trip to the back room
.. to ask the boss for permission to lower the price of a diamond, may be a tactic. If the sales person took a $5,000 1 carat VS1 to the back room and returned with a 1 carat VS2 and said, "The manager authorized me to sell you this diamond for $4,000!", look very carefully.
It is a common tactic that may not be illegal, but in my opinion it is very unethical.
If you suspect that a salesperson might have done this, ask very bluntly, "Is this the same diamond I was looking at earlier and does it match this certificate?"
If you hear any answer besides an unqualified, "Yes!" .. walk away from that dealer. If you hear an unqualified, "Yes!" .. ask to have the gem reweighed and look carefully at the last digit of the carat weight. People do tell fibs.
Back to buying engagement diamonds