Weddingbee boards

My sister recently got married to a nice guy. The week before the wedding I met his mother who I had talked to a little bit about helping with last minutes things. She was supposed to call me to do the flowers and never did. I figured she forgot and it wasn't a big deal. Next, I was working on the seating chart. I told my mom we didn't have enough tables which caused a huge argument (my mom was stressed). I turned to the MIL and asked if all her tables were full and she said yes. I noticed a smug look on her face- but I thought it was just me being sour. Later that night when I really went through the chart the mother in law had 4 tables with less than eight people causing the shortage. I also acted as their photographer- I asked everyone to be at the house by four for portraits. The MIL and her family didn't show up and everyone turned off their phones (which is very odd). There were a few other incidents, but the icing on the cake was she snapped at my husband at the end of the night because he was checking her husband's jacket to make sure it wasn't my brother's. It was really odd.

 Needless to say, I'm not fond of this woman and neither is my sister. Today I log onto facebook and see my sister suggested my husband and I friend her mother in law. I'm irritated with my sister and her behavior is irrational. I'm friends with my MIL on facebook, but my family is not fond of my in-laws so I haven't suggested they friend her.. It doesn't make sense to.

 So here's the question- should I just friend this woman or talk to my sister about not friending her (I feel like this is going to cause an argument).

I would ignore the suggestion.  I don't even understand why there has to be an argument with your sister about this? 

Just ignore the request and don't bring it up with your sister. If she brings it up to you, you can just say "mehh... I'm just adding people I'm really close with on FB now".   End of convo :)

The argument is going to be one of those things where she is upset because she knows she was wrong to do this and it's stirring the pot. I know she's going to get defensive. I don't even get why she did this- not two days ago she was telling me what a sociopath this woman is and I told her how i felt about the wedding/how I didn't want to be involved with this woman.

 I don't have many facebook friends, I know and mostly like everyone on my list. I think I'm going to go with ignoring it and I'm not going to say anything to her.

 I'm def. not going to confirm her. Not sure what to do about my sister,I think she's just being a drama llama.

I would just ignore and if she brings it up, tell her the truth, you don't want to and refuse to get into it past that. Why should there be an argument over this?

@bklynbridetobe: right above your post is an explanation of why there would be an argument.

Thanks everyone.