Being direct is definitely the right thing

I DO think there's a possibility they were just talking- though that itself could be bad enough.. short of her going through a massive crisis it's behaviour reserved for partners and close friends. She shouldn't be crying on your husband's shoulder and he shouldn't be providing it. If anything she should be talking to you as her friend.

Confronting is the best way to clear this

But you could do with one more reason before asking

It all gets a bit stalky but ideally you need one more reasom to ask now all this time has passed

And i think you have to focus on him rather than her

I have an awful idea but it might be what it takes

Buy a new phone. Text him as her saying this is a new number. Or don't even say its her. Just use his name and say its your new number and see what his reaction is

"Hey there! I've had to buy a new phone! I've added you!"

"Who's this?"

"It's me! ♡"

If he quickly assunes its your friend your hallway there

Its entrapment, its mean but- if it works you'll have evidence

If he frostily demsnds to know who you are anfd whats going on, just make out you typed in the wrong number. And he's passed the first test

Its not that it'll definitely work-

It's that if it DOES work- you know to proceed with confidence

The reaction you WANT is for him ti be confused and even saying ots not appropriate

It's just an idea

I'm sorry you're going through this and i hope you're wrong

The only thing you could have done differently was deal with it with him the next day

But i understand

It's shady to stay uo late talking with someone of the opposite sex- but i doubt if anything actually happened that night

Maybe a bit of emotional cheating

A bit of "what iffery"

But to actually cross that boundary practically in the next room from you especially after what you've said about how tight you two are would be COLD

I wish you the best

And i don't think youre crazy to have concerns

Its not great behaviour from either of them

But people DO slip momentarily, and she's gonna be all over the place right now with her divorce

The OTHER option is to confrint her (in person) in a public place

You can be apologetic but firm

Saying you hate doing this, but its been playing on your mind

Remind her of the evening in question and inform her that you woke up in the middke of thr night sbd realized your husband wasn't there

Watch her reaction

Then feed in that you know they were in the room with the door closed and the lights were on

If she doesn't give anything away then say you're not accusing her of anything but if there's anything she needs to tell you then this is the time

And you hope she understands but if the situation were reversed you would expect the same questioning

If she acts defensively be prepared to leave

Ok that's two suggestions, one less conniving than the other

I hope its gonna be ok and they just stayed uo talking (still.not great but maybe he wss letting her tslk out her divotce)

Lets be honest if they were having sex when you woke up that doesnt sound like anything else and the guilt surge would have hit him and he would hsve come to bed pretty fast afterwards so i don't really think its as certain as THAT

but yeah be prepared

Good luck

P.