Client wants me to walk her dog for 45 minutes each time. Does she get charged 2 times as much?

It's essentially up to you and what you feel most comfortable with. Because it's over the 30 minute standard, feel free to charge whatever you think is best over that time frame. Some would charge 1.5 or an additional fee per 15 minute bracket over. For example, I'd charge $5-8 per 15 minutes over 30 minutes. I.e. If 30 minutes = $15, 45 min = $20, 60 min = $25. It's up to you - just make sure to communicate it to your client :)

Since walks are for 30 minutes each, you would be charging 1.5 times your regular rate. You will have to do this as an adjustment. Be sure you explain this to your client to ensure they understand. It is better to use the modification method than change the number of walks due to not only Rover's insurance provisions but also the new report card. If you don't do the number of walks per day, you may not be paid.

I personally would not charge double for 15 minutes extra of walking time. You can adjust the cost to a price you are both comfortable with.

It just depends on what you want to charge. I charge 16$/30min walk and 22$/60 min walk, so I would probably charge 20$/45min walk because that's what I want to charge. It's all up to you! you could just add half your price for a 30min walk (1.5 times) or charge 2 times. I only provide walking services for those in my neighborhood, so I don't have to worry much about travel time to and from which is why I am not too concerned about offering longer walks :)