Conflict of Interest?

From Jan-June 2021 I did 11 coaching sessions with Client A. Some of what I coached this client on was in regards to a past breakup from a relationship she had been in for 10 years.

Client A referred me to one of her friends with whom I had a consult call, but she did not sign up for any sessions at the time. She did refer one of her friends to me though, whom I will refer to as Client B.

From Aug-Dec 2021 I did 11 sessions with Client B who wanted coaching on a past relationship. In our 3rd session, I became aware that Client B was the woman in the 10-year relationship with Client A.

Wanting to be transparent, I told Client B that I had coached Client A in the past and that if she felt it was a conflict of interest, I would be more than happy to refund her if she no longer wanted to continue our coaching together. I explained to her that all coaching I do with any of my clients is 100% confidential and I do not share any client information with other clients nor anyone else. She decided she wanted to keep coaching with me, but told me she would prefer I not tell Client A she had coached with me. I told her that my sessions with Client A had ended, so I was no longer even in communication with her at the time.

Just today, Client A reached out to me again asking for more coaching. To my knowledge, Client A does not know that I coached Client B. I’m not sure how to handle this situation. I feel I need to be transparent with Client A, but don’t know if that’s breaking any verbal confidentiality agreements with Client B?

I want to handle this professionally and respect the confidentiality of both Client A and Client B, but I honestly am having trouble deciphering what the right thing to do is. I have not coached nor communicated with Client B since our last session in December of 2021.

My 2 options as I see them are:
Option 1: Tell Client A I can coach her again, but be transparent with her that I had coached Client B.
Option 2: Tell Client A I’m not available to coach her at this time.

Any help/feedback you can provide me on this would be greatly appreciated. Thank you!