Help please!

I don't mean any of this to come off ungrateful, I soo appreciate what she's doing.... But a friend of mine keeps giving me hand me downs for our baby and I don't want them. I have no problem with hand me downs but she's getting them from yardsales and stuff and I'd rather know where they come from. When my husband and I first started trying to get pregnant I put away money every month for baby stuff, I know it sounds like I have my nose in the air, but I want to get new stuff that I can use again for our next baby (if we can have one) and we're prepared financially for that... How do I nicely ask her to stop? Any suggestions what to say?