You'd be best checking and cross-referencing answers with other Karoq 4x4 owners, a good specialist tyre fitting place, VWŠkoda (somehow). My thoughts might be wrong so need checking, but @Carlston might know better. It might depend on how old and worn tread the other three tyres are compared to the new fresh replacement. If part-time 4x4 then generally it might be at worse changing both tyres on the axle with the tyre that needs replacement, or if the unaffected tyre on that axle isn't very old and not much tread wear, and wear even across the tread, then perhaps only the one tyre is needed. Permanent 4x4 would be get away with one or need all four, I'd guess. But if you really need the 4x4 facility, if only occasionally, you might be better not risking anything on your wife's car and fitting four new fresh tyres rather than you getting the blame if changing only one or two tyres and then your wife had issues using the 4x4, or lend her the Subaru and you wade through with the Karoq.