The first card is the Nine of Wands. This card represents the end of a certain cycle and symbolizes something that is about to come. This is a major change, something you need to acknowledge. In regards to your question, this card suggests that you may not be able to win your ex-girlfriend back. The end of your relationship was inevitable and by now you need to accept it.
The second card is the Eight of Pentacles. This card indicates that you are on your way to achieving your goal, but still face some difficulties. You have to be strong and persevering to overcome the challenges life will throw at you. You must have confidence in your abilities and skills to achieve your goals, so the answer to this aspect of the question is yes: there is a chance that you can win your ex girlfriend back, but you will have to fight for it.
The last card is The High Priestess reversed. This card speaks of prudence and balance. The key message of this card is that informed decisions must be made based on accurate information. Before making a decision, you need to make sure you know all the relevant facts so that you can make an informed choice. In relation to your question, this means that you need to do some extensive research before deciding whether to try to embark on a reconquest attempt or not.
After analyzing the three cards, we can conclude that there is a 50/50 chance that you can win your ex girlfriend back. However, before deciding whether to take an action or not, you need to consider all relevant facts and gather as much information about the situation as possible. So based on the papers consulted, I'd say the most likely answer to your question is "No."