No, You are not being unreasonable,,,, BUT I'm afraid your friend might not see it that way...
My then-best-friend had her hen party and wedding abroad. I did make her hen party (but only part of it, which she was unhappy about) and missed her wedding because it meant spending a week out there and kids weren't invited, so I couldn't even bring the DSDs and make a holiday out of it...
She never really forgave me missing her wedding and I know that she did think I should have gone for the week without DP (Now DH) and DSDs and would have had to get someone to mind the dog for a week...
We're still friends, but not 'best' friends anymore IYKWIM....
If I'm honest, I'm still sad that I wasn't at her wedding, because we were such good friends beforehand and had been for so long, but then I also know that there was just no way and there was no compromise on her part....
I found out later she'd had a party back in the UK to which I wasn't invited because 'she knew I wouldn't make the effort'....
Hoe you get it sorted.