Competitive jealousy

As I have mentioned before, my SIL and I don't share a very healthy realtionship. We get along, but we have a bad history and there is always a competitive atmosphere in the air between us. I can clearly remember the day I found out about her pregnancy. We used to work for the same company and I found out via sms the previous night. I kept my cool and pretended that it wasn't much, and then when I arrived at work the next day and saw my friend Mariella, I just burst out crying and wept in her office for about half an hour. Mariella is old enough to be my mother and we share a close bond. She understands these kinds of things and she is always very outspoken about what she believes. Well, when I saw Mariella and she could see that I was upset just by looking at me it broke down my invisible wall of defense and I just wept. You see, I was the one who always wanted children. These people were always partying and getting drunk every weekend and their main financial priority was having money for their weekly braai.
Anyway, they were determined to have the first grandchild in the family and they succeeded and I have worked through the feelings of jealousy and I have a fairly good relationship with them these days, but I still sometimes get the feeling that they rub their "having-a-daughter-success" in my face.

To give you an example, I have a BFF called Hetta and she shares her children with me unconditionally. We visit them regularly and she always includes me when it's feeding time or bath time. My SIL on the other hand can't even stand it when I hold her child. Yesterday, while we were visiting my MIL her little girl who has just recently started to walk, came up to me, I picked her up and we played a hand clapping game and the little one was laughing out of her belly while we were playing. Out of the corner of my eye I could see SIL getting really upset. She grabbed a tupperware holder with cheese curls out of her bag and started calling the child's name while trying to get her daughter to come to her. I put the child down and she promptly started to walk towards her mother. I am not jealous of her child but she is forever jealous if her child is sitting on my lap or if I make her child laugh. It's absolutely ridiculous. This is just one of many similar experiences I have had with them and it makes me very angry. I just want to stay away from them.

She also doesn't feed the child any kind of real food. M is allowed to have a bottle, yogurt and the custard range of purity. I have lots of other friends whose children are on solids already and eating from the same food as their parents in small amounts, but my SIL believes that her child will get fat if she gives her any solid food. Come on woman!! My SIL is also very thin herself and quite obsessed with being as thin as possible (she was dieting during her pregnancy and weighed 6 kg's less after the birth than she did before she got pregnant) so I guess she wants her child to be like that as well. I keep my mouth shut, but it makes me so angry! I don't feel any of these feelings towards any of my other friends who have babies, so I have asked myself lots of times before if it's just me. I don't think so. She constantly sends me every picture she takes of her daughter by e-mail, but when we are in the child's presence I am not even aloud to hold her? She keeps on talking about the fact that her next child MUST be a boy, etc, and then I just sit there and wonder how simple her life must be if that is her biggest worry in the world. Are these people from another planet? Maybe I am just too sensitive. My MIL is also not helping because she is forever telling me how perfect M is and what a wonder child she is. I know she is very cute, and all, but I do sometimes wonder how my own children will be measured up. I kind of feel like I want to keep my own babies (when I have them) away from these people, but DH will be hurt if I do that, and of course my children will suffer because of their mother. I just don't like this competition and it's exhausting. Sometimes I even contemplate moving to another town to escape it. But running away won't solve our issues. I tell you, I am just so tired of trying. And it's damn hard to cope with all of this without letting it affect you. I want to do the christian thing and just turn the other cheek, but I am upsetting myself and I am starting to hate these people.