IPA: /ˌoʊvərsəˈspɪʃəs/
KK: /oʊvərsəˈspɪʃəs/
Having an unreasonable or excessive level of distrust or suspicion towards others or situations.
Her oversuspicious nature made it hard for her to trust anyone.
Oversuspicious → It is formed from "over-" (meaning excessively) and "suspicious" (from Latin "suspiciosus", meaning inclined to suspect). The word describes a state of being excessively inclined to suspect others or situations.
Think of being 'excessively' ('over-') 'inclined to suspect' ('suspicious') — that's why oversuspicious means being overly wary or distrustful.