IPA: /ˈoʊvərˌspɛndər/
KK: /ˈoʊvərˌspɛndər/
A person who spends more money than they should or can afford.
She is an overspender, always buying things she doesn't need.
Overspender → It is formed from "over-" (meaning excessively) and "spend" (from Old English "spendan", meaning to expend or use money). The word "overspender" refers to someone who excessively spends money beyond their means.
Think of someone who spends money 'excessively' ('over-') — that's why an overspender is someone who spends too much.
No commonly confused words.