It can be. Some of the girls are in demand and they know it. You can always negotiate. 25 and hot, like that one, can command escort level prices. Also, for two hours, standard is 2 pops before meal break. And for a good meal, they would gladly stay over the 2 hour mark. Just make sure you get the 2 pops in first.
I definitely would not pay an extra 2000 baht for some walking around, hand holding, and small talk over a meal. Lesson learned. Next time I check out Thermae, I'll do only 1 hour to get a feel for the girl. If I really like her, I'd come back the next day and do longer session times.