Jane works in the sales department of a service company. she has impressive interpersonal skills and always turns up for work on time. though she gets along well with her coworkers, she has a habit of constantly interrupting them during a conversation. which core business etiquette, is missing in jane?

Good communication skills are missing is Jane's etiquette because she is not honest and confident enough to  her colleagues.  

Explanation:

Although Jane has good and impressive interpersonal skills, she should not interrupt others during the conversation because everyone has there own ideas and own mindset.

It is true that she is very co-operative with her coworkers so instead of interrupting others she should motivate others thoughts and ways of figure out the ideas.