General Nonimmigrant Visa

My sister is in India and the prospective groom is a US citizen. They have concerns about how to proceed with marriage and relocation of the girl to US in a timely manner (prefer not to wait more than a year for marriage/ living together post-marriage for personal reasons) Current fiancé visa processing time seems to be 15 months. It was not this long pre-covid, realistically can this processing time reduce this year? If they do marriage in India first, what’s the quickest way for her to come to US and how long would it take She has a valid B1. Can she travel on that to US post-marriage for 5-6 months only without any risk to her green card application? She is trying to get an L1-B visa through her current company. Will that visa approval be affected if they get married in the meanwhile? In short, what is the quickest path for her marriage & relocation to the US right now?