To think my SIL hates me for stealing her limelight

[MissPollyHadADolly19]

Me and SIL have had a fantastic relationship throughout mine and DHs marriage, when she was pregnant with her DD and after the birth we was even closer, we would talk every day and see eachother whenever possible.
Then I found out I was expecting in December and have seen her all of twice since and mainly by circumstance rather than choice, probably speak to her once in a blue moon and not once she has asked me about the pregnancy or even how I am in general.
As it is she's her DMs "favourite" and her DD is the only grandchild, which I believe SIL thought would be the case for a long time due to the fact I have had fertility issues and none of the other siblings have or are likely to have any DC in the near future. SIL quite likes being the centre of attention and is now well aware that because I am also having a DD that she is going to lose centre stage, for reference mine and MIL still have a good relationship. MIL also provides SIL with financial support, childcare, housing and everything inbetween - I don't expect any of this but obviously SIL must think otherwise.
Am I being over dramatic or is my SIL being abit of a brat?

Gosh MN is just plain unpleasant sometimes!
It does sound very strange OP. Is it worth writing her a letter? Something has changed.

Jeeeze, don't even THINK of sending a scan picture!

I know this must be upsetting. Someone I was close to has cut off contact without giving any reason, and it's really upsetting me. It's absolutely normal to look for reasons and want to mend things. But your SIL seems to be a very complex person, so try not to take it too personally. I feel your pain though.

BUT DON'T send the scan pic!

I'm definitely taking note that sending the scan pic may not be an idea, still going to send to MIL as usual but as I would normally send it to SIL too would she not then think I'm excluding her? I don't want to come across as tit for tat which is why I am trying to still involve her in the same way I would before. For the PP asking how long ago I told SIL, it was the day I found out so Xmas day.
Also yes MIL has played a big part on why SIL is how she is, I love my MIL but I totally disagree with how she bought up her kids and it's only now they're all grown up she probably regrets it herself - obviously still won't change though.
I wouldn't really think it was because of me being married to the brother she dislikes but I guess it could be her anger towards him having a happy life rather than actually at me. I had hoped our friendship was more than me just being her SIL though.

Congratulations on your pregnancy OP

Maybe SIL is embarrassed or ashamed that her marriage has broken down, perhaps she sees it as a big failure on her part (even if it isn't), perhaps her soon to be exH is going for custody of the DD, and meanwhile your situation is very much improved with your happy baby news. Or, perhaps she is not interested in you now that your main focus will be your much-longed for baby, and not her. Whatever it is, it is hard when a friendship suddenly cools, and you miss the person you were friends with. These things often go round in cycles, so just try not to do anything inflammatory and it may all come good in a while.