'She asked for x and you got her something similar and cheaper y and expected her to be pleased?
If you could not afford x then you should have bought a voucher for the shop that sells x (to the amount you could afford, not the whole value of x) so that she could top up the difference and get x that she wanted. She didn't want y. '
You're the so-called friend, I see. This type of entitlement and childishness, 'WAAA! I didn't get what I demanded you get me!' is unbelievable in any adult.
Instead of doing this, OP, you could instead tell her, when she tells you to get her something, 'You know, I think the time has come to stop giving each other gifts.' Or better yet, just stop getting her presents!
Just don't even bring it up. If she does, then you tell her, 'I don't think we should exchange gifts anymore.' Send her a digital card.
Some people think the world owes them what they want on a silver platter.
Your friend is rude and entitled.