Welcome to the forum, this is an excellent question. Before I answer it let me first say Beebs gave you the advice I would have given you about switching to Beanut Butter, it's zero carb and very tasty. You can also use my crunchy peanut butter recipe in the book to dramatically reduce peanut butter carbs. Now to your question.
The answer is yes and no AND it's complicated. Many times type one diabetics are taught to add together total carbs in a meal and subtract total fiber to help arrive at the amount of insulin they should take prior to eating. This would tend to make you believe that fiber can negate any type of carb....but that's not true. Carbs that metabolize quickly like the added sugar in your peanut butter will not benefit from the fiber in the celery but the carbs from the peanuts which metabolize more slowly will. Trying to keep track of the process is tricky and cumbersome and should not be attempted unless you are an insulin taker and need to go through the process to determine dosage.
The FAT TO SKINNY program makes you accountable for each carb you consume and credits you for each gram of fiber for that particular food. This is the easiest way to keep track of your max 20 net carbs allowed each day.