We don't say 'lack in': only 'lacking in'. In the phrase 'she's lacking in manners', the word 'lacking' is a predicative adjective. The collocation goes like this: be + lacking[adj] + in + noun. When we use the word 'lack' as a verb, it takes a direct object (no preposition): 'She lacks manners'.

нет такого сочетания если существительное то lack of если глагол то просто lack

No. See my answer below!

Can I say, The lady is pretty, but she lacks in manners?

Lack in something means not having something. Russian translation of the same tech provided by Candice in that thread: Девушка красивая; но не хватает воспитания (дословно нет манер).