Was I right to do this?

im still in a group chat that hasn't been used for ages. In this group chat is my ex and all her friends, who became good friends of mine too.
One of the friends posted in the chat suggesting to have a night out. Obviously I read this, because the chat haven't been used or ages it just lay dormant.
Now that I have split with my ex I have lost my friends too because they were her friends really and she introduced them to me. So having a night out with them is obvs something I won't be going to.
instead of ignoring I jut wrote that I hope they have a good time and that everyone is doing good.
obviously my ex will see this.
do this think this was ok to write? Or being to intrusive because it involves my ex?
Was I right to do this?
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