Yes, my heart truly breaks for the OP that she was invited to a wedding by her friend... What a truly hard position for her to be in.

It doesn't mean she's frustrated or stressed with you. There are other things in her life that could stress her out too. If you're worried about her invite her for coffee or dessert alone sometime. And don't get offended when she can't (again, she could just be stressed out and tired with no relation to you at all).

This is some HS bullshit.

Not everything is about you. Maybe she's just fucking busy, maybe the run up to the wedding is stressful, maybe she has work issues, maybe she has health issues, maybe she's just tired... you have no idea because none of it is your fucking business... Be a good friend and be empathetic of your friends who seem to be a bit more withdrawn for a time; and then eventually I'm sure she'll come around and things will change for her. But, if you seriously can't find an empathetic bone in your body then just skip the wedding and save this poor woman from your drama filled head.