SP asked me out but there’s a 3P

Hi guys I’m manifesting my SP (ex) and in the last days I’ve been seeing a lot of movement. yesterday SP responded to my ig story about tennis asking me to play tennis together and wishing me merry Christmas. But I know SP has a new girlfriend and has recently made it official even on social media. And I don’t want to go out with SP while in another relationship. What should I respond to the messages? Should I accept even if it goes against my morals?