Dear LIB readers: Should I warn my ex?

From a LIB reader

I need impartial advice from your readers please. I am a female who has been involved in a long distance relationship with a man in Nigeria, I live abroad. I have visited him over there and he has visited me here. However, I have always suspected there was a personal relationship between him and his female business partner, who is older than him and married too.

I even saw text messages on his phone from her, messages only a lover will send, but he denies any wrong-doing and says there is nothing personal going on between them.

This older woman lost her husband 7 months ago, and with me not being around, I believe their affair intensified over time. I had an encounter recently with this lady and I decided the guy was not worth my time so I ended things between us. I have cried and prayed a lot since then and one thing keeps coming to me, that he is under the influence of some kind of evil power of this woman's doing.

I want nothing more to do with the guy, I can never get back with someone that sleeps with another man's wife, but I feel like I need to warn him about this woman.

Should I say something or should I leave him to bear his cross?