am I overreacting? (long, sorry)

ok, I need your advice bc FH keeps telling me that I'm overreacting. Here's the situation... FH and I have been engaged for 3 1/2 years. We recently, about 6 months ago, finally decided we were ready (financially) to start planning the wedding. We are still kinda young and have to pay for EVERYTHING ourselves. Anyway, so in the mist of us looking around for RH's - FBIL gets engaged. I was so happy and thought that it was going to be fun planning our weddings together. But, it hasn't. FSIL is pretty young and is the first in her family and friends to get married, so she doesn't know much about weddings. I've tired to help by telling her my thoughts and ideas for my own wedding, but now I'm getting frustrated.
First, FH and I book a day and RH. a week later, she books a day a month after ours - which I was okay with until she made it clear that she was actually annoyed at us for booking our date in the summer when she wanted the summer, (ps since I've known her she always said she wanted a fall wedding). Then she tells her even younger sister (MOH) that she has to plan the BP and shower around my dates, so I have her keep asking me when mine is going to be. I have no idea!! It's a year away!! They want me to tell them or they are just going to plan it. Whatever! And now, we both ordered STD's, we talked about this two weeks ago, that she was going to wait another month or two bc it was too early and to let her know when I send mine out. This would make sense since my wedding is first and her's is still over a year away (08/08). I get the mail the other day and guess what's there.... yup, her STD's. I just feel like she's rushing to do things before me. Am I taking it to far?? I have no problem having our weddings close, but isn't it just common curiosity to understand that since FH is older, we have been engaged longer and our wedding is first that she should allow me to do things like this first? I'm not sure if I'm overreacting, but I just get the sense that she's not happy that our wedding is first, so she's doing everything before me. P.s. - she already picked out invitations, I'm sure those would go out well before mine as well. What do I do here??