How should I react?!?

by Shelly
(Mesa, AZ)

Here's the situation.

I have had the same best friend, G, for over 20 years. We've shared everything from children to layoffs.

The problem is this. My sister and I had a falling out about 8 months ago. 3 months ago, we mostly patched things up. My sister thought that she would "get back" at me by making an effort to become G's new best friend. It started with my sister asking her to go do things and then getting the husbands together. Now, they are together all the time. I used to be invited to G's home whenever there was a get together, now my sister is. It's as though she's taken my place and G has no room for me in her life. They often talk about their adventures on their blogpages and Facebook and it's very hurtful to me.

How should I react to this? I don't want to seem petty, but it's really hard.