I'm a florist, and pictures are SO helpful. However try and narrow down something like a colour scheme or a style you like and take pictures of those only.
I see A LOT of brides who have enormous Pinterest boards of image after image of things that they 'sort of' like, and those consultations are long and meandering and we both end up confused.
Be ruthless: if you want pink flowers, delete all the images of yellow roses that you saved because you liked a particular piece of foliage in that photo.
The flowers will absolutely cost more than you think. Supermarket flower prices over the last few years have made independent florists prices look high in comparison. Floristry can be very labour intensive, and there's no way to cut corners. That said, there are some chancy fuckers out there who will charge what they can get away with.
A good florist should be completely transparent regarding prices - you should be able to ask for a breakdown of costs and not get fobbed off.
Also beware Brexit. Prices are going to skyrocket as most of the UKs flowers come from Holland. Make sure you discuss what contingency measures she has in place for the possibility of your flowers not being available, or a sudden hike in price when she sees just how much Holland will start charging us as a captive audience. The UK does produce flowers, but they are very season dependent and there won't be enough to go round if there's a Dutch shortage.