Weddingbee boards

Ok so after much consideration I asked my future sister-in-law if she wanted to be a bridesmaid.  So far the only communication I've had with her has been on facebook since I don't have her number and she doesn't have mine.  Her husband is my fiance's brother so she's going to be at the wedding anyway. She asked me where the wedding was going to be and she would write be soon.  My issue is that she hasn't answered my question yet....I dunno I guess to me its easy to say yes no maybe so and ask questions so I can give the other person some kind of answer but so far nothing.  It's only been 4 days since I've asked.  I sent her another message asking if she decided anything and to call me for more information so she can make a decision.  Plus I gave her my cell.   

I saw her make a couple posts on facebook so I guess that's why I'm a lil in disbelief about the situation - like you have time to post but you can't give a simple yes or no.  It's not like I'm trying to blindside her into being a bridesmaid - I want to tell her the details - Its just I need to know so I can stop racking my brain lol

:::sigh:::: am I overreacting????  Has anything like this happened to you?  What should I do?  

thanks for the advice! she finally responded with a yes! woooo now i don't have to freak out anymore lol