US Immigration from Serbia

Okay, here it goes:

The beneficiary/my fiancee is a Serbian citizen and has two US visas pending now: first she applied for a tourist visa to the USA last June (which has a waiting time until 2023). And we also have a K1 visa pending since last September (because we're to be married, obviously.) She works for an American company and her boss, who is American, wants her to come to a conference in the USA and is willing to give her a business visa recommendation.

My question is, should she opt for applying for the business visa? Or would this be risky and look like she's "visa shopping?" What ever the case may be, I don't want our K1 visa denied because the officer saw she applied for two other visas. If you don't know, Serbian citizens are considered "high risk" and it's more common than not that they get denied.

We are also willing to cancel her tourist visa, because it seems like the K1 will be approved before that anyways. But she has no other way into the USA and I would love for her to meet my parents once before we get married! So this business visa could be a really great opportunity if there are no risks with our K1. Any opinions would be GREATLY APPRECIATED! Thanks.

I know I can Google this, although I would like a straight answer from someone in the community instead of a government website:

Basically, with the K-1 visa you and your fiance have 90 days to get married in the States. Once you are married, can your fiance stay in the US indefinitely? I assume this is the point where most beneficiaries will apply for their marriage--based Green Card, but while the Green Card is pending, the beneficiary can stay in the US, right? Basically what I'm asking is, after the 90 days are up, the couple can live in the USA indefinitely?

I would hope that USCIS would allow anyone with a Ukrainian fiance to now file for an expedited application. But knowing USA, that probably wont happen. My fiancee is Serbian but I can't help but feel sorry for those who are in Ukraine and might have to suffer consequences from the current events.

Does anyone else have this situation?:

Basically, my fiancee lives in a country where it is EXTREMELY hard to get any kind of visa to the USA. Therefore she cannot meet my family or we cannot visit my home until our K-1 visa is in our hands in order to get married. I have to live with her in her country because it's basically physically impossible for her to get into the USA. I just wanted to know if anyone else is/has been in this situation. It really sucks that we cannot simply visit my home together for her to see where I'm from, meet my parents, etc and have to wait ridiculously long just for our NOA2. So frustrating!!

Is anyone else seeing this? Just refreshed the USCIS processing times for i-129f/k-1 and they're currently processing cases from the 11th of Feb, 2021? A few days ago when I looked they were at the end of April. Anyone know what is going on? Is this really true?