SHOWER PROBLEMS

Major etiquitte issue here -- my sister is pregnant with her first child -- due in the beginning of March. Ever since we found out, the understanding was that I would be giving the baby shower. My sister's boyfriend's mother wanted to be involved as well, but when we spoke on the phone to see how we could do the shower together, she was totally uncooperative (said she wanted to "throw" it, but wanted me to pay for it because her family was "poor", etc., said it would take her a while to get the addresses of her family for me to send the invites to because she had to write them because she couldn't afford long distance (how much sense does that make?). We finally agreed that we would have the shower at my place, and that I would foot the bill for everything (decorations, food, etc) and that all she would need to do is give me a list of the people to send the invites to and they would just need to show up. We even went as far as setting a date. Let me mention, too -- that the majority of the people who were supposed to be coming to this shower are from his side of the family.

Anyway, fast forward to the past week. My sister calls me, tells me that she has bad news, that her boyfriends mother called and said that their family wasn't going to the shower I was going to throw, that they were just going to throw one themselves, and that I am not invited. Said she was angry at his mom, but she wants to go to the shower so she can get the things she needs for the baby. I put on a brave face on the phone with her, told her to go ahead and have a great time at her shower, etc..

But I'm really hurting bad -- my mother isn't being supportive at all -- says I'm in the wrong for being too petty -- that I should have shut my mouth and let her throw it in the first place and paid for it. I'm upset because this would have probably been the only baby shower I'd ever have given/attended because a) I don't have any friends, b) sis doesn't plan on having any more kids and c) I'm infertile so I'll never have kids of my own. I think most of the hurt is letting it fester because I'm not taking out on my sis (its really not her fault) and I just need to vent it out.

Here's my questions, though:
1. Who is in the wrong in this situation -- his mother or me??
2. Should I just wait until after she goes to the other shower to get her what I was going to get her?? Since I'm not invited to the shower (nor would I want to go under the circumstances at this point anyway), and since I'm planning on getting her most of the big ticket items, is it in bad taste to ask her what she's already got so I don't get duplicates?? Or should I not get her a gift at all (I've already given her several things for the baby throughout her pregnancy -- if I give her the other stuff, should I present them as "presents" or just hand her the stuff like I have been all along -- it would seem sorta weird to give her wrapped boxes, etc.

Anyway, sorry to ramble. Just really needed to get this whole situation off my chest.

Becke