I have been interviewing at two companies, A and B. I started interviewing with A earlier than B. By the time B reached out, I was nearing the end of the process with A, so I asked B to expedite their process.

B was accommodating. I have told B that I expect an answer from A yesterday or sometime this week. The recruiter at B asked me to be transparent with her about A, and that if I pass the last interview, B could potentially give me an offer by end of week. Last week I was also told that B is still early in their pipeline of candidates.

Now A has gotten back to me and told me they went with someone else. So my question is: what do I tell B?

I don't want to lie to B, but I also don't want B to slow down their process if they know that I no longer have a competing timeline/offer.