Why are family relationships so complicated?

I won't lie, I was a daddy's girl. But I do love my mom dearly and even though we aren't as close as I would like, I thought she would be excited about my upcoming wedding. She isn't. Not because she doesn't support the union or isn't happy for me, she is, but why can't she be bothered to come over and see my dress? or talk to Craig (via skype)? I've asked and asked her, to the point of now I get no response anymore from her at all. Ok. I get it, I wont ask anymore. Maybe i'm being a pest but i'm excited and I want her to share in the experience with me. I want it to be something special for her too, something we can bond over. Several weeks ago when I asked her if she was off work, she said 'no, I have a wedding trip to pay for'. Ouch. I cried. Then she didn't understand why I was upset, she said I took it wrong. Maybe i'm too sensitive.