Of course you are feeling lonely and left out. The wedding will have been a hugely emotional occasion and now it is over I can understand how flat and empty your life could be.
I came home after youngest D’s wedding and just cried- because her husband is lovely, she was so happy and because everything had gone perfectly, but most of all “anti climax ”
You have even more reason to feel that letdown as you do not have her father to share how you feel, but also because she has “joined” as you see it, a large and loving family.
But of course she is still your daughter and has not left you.
Do try to be glad she is happy and gets on well with her in-law’s and if you can possibly find some other activity, or treat for yourself or maybe a short break to take your mind off it for now, it could help.
You might like to write down how happy you are for her, how much you welcome your SIL and know he will look after her and perhaps how proud her dad would have been and wish them all the happiness in the world.
And then when they are back, invite them round for a family meal, make a huge fuss (in a nice way) of your SIL and do not let on in the tiniest way that you have ever felt jealous.
Believe me, I have been there and know from my experience that jealousy is the most hurtful and destructive of emotions.
Don’t go there! ???