Meeting up with an ex, she is having dinner with friends tonight, and i will see her tomorrow night. she will take a rapid covid test tomorrow before seeing me, if negative am i likely safe from exposure from covid?( we will prob have sex?

Hard to know: This is a common way people are screened for entry into sensitive areas. However, there are false negative & false positive screens. Any intimate contact with another is going to expose you to any disease she carries whether known or not. That's the chance you take to live life to the fullest. Luckily at your age the risk of a fatal covid case approaches zero. Treatments are also improving daily.

COVID 19 testing: The COVID 19 antigen test is not as accurate as the PCR test. There are no guarantees. However, the scenario is safer than many other situations if she has a negative test result at that time.