Since you only gave her 1.75mls the last time and it had no effect i'd bump it up a little. You can go slow and bump it up a little until you get to the max dose and if it doesn't work by then you're better off not going any higher. try giving her 2mls next time, then 2.5, then 3. you want to go with the lowest working dose.
Also just wanted to mention that there are these shirts/wraps for dog anxiety. I bought the
Thundershirt | The Best Solution for Dog Anxiety for Morgan because she's scared of thunderstorms, fire crackers, loud noises, etc... She's doing really well with it. Every friday night the nearby college has a baseball game in the spring/summer and they set off fire works afterwards. The past few fridays i didn't have to put the shirt on her. She was aware of the fire works and came to lay down next to me but she didn't shake or pant (which she usually does). so we're making progress.