I do this exact thing with one friend.
Our kids are 9 months and a couple of dress sizes apart.
I inherited a bunch of baby clothes from my siblings (5 nieces and a nephew) and she got another bunch from her sister. My daughter wears a lot of her niece's clothing, her son a lot of my nephew's. Or things like snowsuits, sleeping bags, onesies... We've marked the tags and things go back and forth as the kids grow.
It works for us, as we each only have one person loaning and all the rest are hand me downs we get to keep. Not too much hassle and we both know that things might be returned stained or forever be lost. And that's ok and we each keep the things we really want to have as keepsakes.
So, no I don't thin she was rude. It would've been better to be very clear from the start that she was loaning, not gifting you those clothes. And, you can decide to either keep track of them and use them, then return or return them right away if it's too much hassle for you.