LOL my MIL is excellent, she does give us lots of stuff (we have about 6 million pairs of booties from her already, SERIOUSLY!)... but my SIL is a bit like this... buying lots of really awful stuff and telling me how things should be done... unfortunately its a grin and bare it situation. My SIL is going to be a first time aunty, so I let her have her fun with buying things, though I do chuck a few hints here and there and we go shopping together.

I agree with Lulu though about MIL in the delivery room... well, I am asking my MIL to be in for there with us but for me it would be SIL... if she is this pushy now, imagine what she is going to be like in there. And at such an emotional time for both you and your DF, you need someone in there who is there for you both and supporting you both, not in there for her own gain and to say she was there and try and hold bub first (sorry, just projecting my own SIL troubles there...).

It is a pain to have overbearing ILs, but it could be so much worse. She might seem to be trying to take over, but she's probably just excited about her first grandchild. Theres no way you can stop the 'advice' (believe me I've tried... ), so yes just smile and nod and let your mind wander.