sister is also pregnant..

Laura
I am currently 11 weeks and 4 days pregnant woth my first child, my sister has a 2 year old little girl. When she found out i was pregnant she told my other two sisters and parents that they best not stop giving attention to her little girl when i have my baby, she also made a comment about my mum paying more attention to me now that i was pregnant. 
On sunday she announces that she is now nearly 6 weeks pregnant, to which everyone was a little disapointed by, her little girl is hardly ever at home with her and is looked after by her grandma for the majority of the week and by myself or her other aunties and my nan, she does work but it seems every oppertunity she can get to have someone else look after her she will, her husband is in the navy and works 3 weeks on then 3 weeks off, and the same thing happens when he is off she spend the majority of her time elsewere.
I feel that as soon as she found out i was pregnant she decided herself that she was jelous and was going to get pregnant, to regain the attention. This being my first child feel like somethings been taken away from me, i feel her and her partner are extremaly selfish!! Am i being stupid and selfish myself, should i see this as apositive and share our pregnancy experience? The babies will be born about a month apart..