Toy Conundrum Leading to Friction With MIL - Advice?

My husband and I are the proud parents of an 18 month old girl (our first). While I was pregnant, we talked at length about not wanting our house to become overrun with toys, as many do these days.

That's not to say that we don't provide toys for our daughter- quite the contrary- but in the interest of a tidy house and wishing to not let a sense of materialism flourish in her from such an early age (as well as gaining appreciation for the things she does have), are trying to really limit the amount of them she has. We are going to try and keep it to what can fit inside a rather large wooden toy box we purchased, as well as a corner shelving unit made for her room by my father. We told all our friends and relatives that books and clothing were preferred but in the case of toys, we requested things that she could enjoy long-term, rather than getting the house full up with a deluge of infant items that she will quickly lose interest in.

This has led to problems with my husband's mother. She has ignored our wishes and continues to buy Rose mountains of toys at every opportunity; from endless claw machine-tier stuffed animals, to big bulky play objects and stations (for lack of a better word, but I hope you can picture what I'm talking about). We have asked her to stop or at the very least, cut down on it and this has led to her subtly trying to hint that we are being bad parents, don't know what we're doing, and are "depriving" her of a good childhood.

My husband and I are at a loss as of what to do. Any suggestions?