Ask why she told you. Where to go depends on her motives. She possibly told you for transparency and so there would be an explanation if she changed her behavior towards you. Overall, I think she may have recognized an inherent incompatibility that makes for a poor romantic relationship but is fine for a friendship, or she's worried that if she got involved with you and it ended poorly, she wouldn't be able to go back to being friends and she values your friendship more than taking that risk
Option four. Tell her that you are hurt that you were left out of the wedding. And you are going to message her brother. To find out why.
Ask why she told you. Where to go depends on her motives. She possibly told you for transparency and so there would be an explanation if she changed her behavior towards you. Overall, I think she may have recognized an inherent incompatibility that makes for a poor romantic relationship but is fine for a friendship, or she's worried that if she got involved with you and it ended poorly, she wouldn't be able to go back to being friends and she values your friendship more than taking that risk