Incredibly trivial- how would you read this?

[CurlewKate]

I arranged a family evening out-but it turns out that ds's girlfriend has to work unexpectedly. It's too late to rebook. I sent a message to ds saying "Do please tell X that we're really sorry she can't come!" Ds replied "She's disappointed too-but there's no need to apologise!"
I wasn't actually apologising- I was saying that I was sad she couldn't come. It really doesn't matter- either interpretation is fine with me. But what would "sorry" mean to you in this context?

As you meant it. But it’s not much of a leap to interpret it as your son did.

Sorry in this context means you were disappointed she couldn’t make it.

I'd read it as you meant it. It seems obvious to me.

Exactly. It’s not an apology!

I guess if he's taking it literally then he may see it as saying "I'm sorry we booked it when it wasn't convenient for your girlfriend, I feel guilty she cannot come" but I'd totally read it as the thing you say when you're a bit sad/indifferent to something happening .

I actually thought you were going to say he'd read it sarcastically. We're SO sorry she can't come (yes!!!!)

@SleepingStandingUp Oh, if I'd meant to be passive aggressive I would have made a much better job of it than that!🤣And she was free when I booked.