Pregnant with mother-in-law problems....!?

Im 36wks 5days pregnant with my 1st. Firstly let me say that I absolutely love my mother-in-law to bits! I really do! I couldn't ask for a better mother-in-law! She is great! Honest! But... she has been on my back since we announced our pregnancy about what theme we want to decorate the babies nursery in because she wants to go and spend money and buy stuff - like mobiles, linnen, wall decor etc. I have told her several times that we are waiting till the baby is born to see if its male or female (we didn't find out!) and then we will decide on an appropriate theme. I also told her that as the parents, we will decorate first and then she can buy stuff later on. I don't want to have to display things just because she has given them to us and I would like the opportunity to decorate with my husband before she goes and fills the room herself. At one point, a Pooh Bear theme was mentioned (but was NEVER definate) and bang... she went and got all this Pooh Bear stuff. Now we'd like to do flowers and butterflies for a girl or trucks and aeroplanes for a boy so all the Pooh Bear stuff will only get packed away. She has told me that as soon as the baby is born she will be going to markets and shops to buy stuff. I REALLY do appreciate it and I can't be happier that my baby will be so loved by her, but I guess i'm feeling as though a life long dream I have had to decorate my own babies nursery is being taken away from me. How do I suggest to her that it's ok to buy stuff, but just not to over-do it. And that if she still wants to buy stuff, clothes and skincare products are great too?!?! Im feeling a little angry about the whole thing coz she has done this 4 times over with her own children and now it's our turn. Is it my hormones, am I being selfish or greedy or is my mother-in-law overdoing it? She already has a 7 year old grandson too.