If you know you are being manipulated, use it to your advantage
Usually, they are trying to sell you something, and may often spout BS to make the offer even more attractive. By using similar manipulation techniques back, you tend to get a much better deal (so long as you at least "buy something").
If, for example, they are offering 25% on your next deposit, tell them you quite like the idea, but unfortunately y casino has just offered 35%, and by taking this up, you no longer have enough left to take up the 25% offer. The sales rep has no idea whether or not y casino really has offered you 35%, but they may fight harder for that deposit knowing that there isn't enough to go around, and y casino is going to get it. You might end up with a 40% bonus that weekend, even though they were trying to sell you 25%. It also means you get to play, because of course it was just a tactic, you haven't yet got the email from y casino with an offer for that weekend
When it comes, you just tell y casino that unfortunately x casino has just offered 40%
In the end, the deposit goes to the highest bidder.
I suspect they use females in order to reduce confrontation. A male player is less likely to be abusive to a female sales push than a male one, and a female rep is more likely to relax an irate customer just through the use of a soothing tone of voice.
One has to remember that no matter what, they are not your friends, they are trying to close a sale, or deal with an issue at minimum cost or loss of profit for the company.