YumYum, I will say take it and make lemonade. I wouldn't take it personal. Sometimes in life people are going through things that we cannot understand. Their actions is not personal towards us but it is something that they need to do at the moment that will be good for them. I say this because right now I am going through the same thing. I have a lot of things going on in my life right now that have been getting me down. Dealing with them in my way is leading me to alienate some very good friends and even my family on some level because I just need to "do me" right now. Maybe that is where your friend is. She said that she was depressed. I don't know if she told you why she was depressed but maybe being all happy and attending happy events is not in the cards for her right now. It sounds like right now she want "to do her", which is just being with her and her dog.
I would say don't take it personal. Just go ahead and enjoy your wedding planning, make lemonade out of the lemons that she has served you, and when she is ready, she'll discuss with you what is making her depressed and why she acted the way she did. I hope this helps. Good luck, Aisha