I have found that sometimes when you delete a bid they come back with a slightly lower offer, but as pointed out this may be the lowest she will go to, I have had a couple of RB's where I actually ended up paying a slightly higher price than I advertised as I really liked the look of the bidder.
If you are sure you don't want to go that high and have another one in mind would always be worth emailing and saying that the you really like her profile etc but you cannot go to that amount at the moment as she may offer a further reduction if she is has no bookings, but as many of the experienced punters on here will tell you always research a plan B just in case.