To be honest, the process will take as long as it takes; and many things could factor into it.
If it takes an excessively long time, it is possible a local US congress person (senator or house) - although it's likely their actual office staff rather than the elected person - might be able to get some sort of response from USCIS. And, if I recall, there is a process to sue any US Government department for a decision of some type (IANAL but I think after a very lengthy period of time, there is a way to file a write of mandamus against USCIS/the relevant party).
In my case, I found that once USCIS started "talking" about in-person interviews and/or biometrics they moved to interview within 6 months of that. Three of my "decisions": the initial denial at the embassy, the subsequent approval at the embassy, and the final adjustment of status were all approved by the officer(s) on the spot, with the formal letters/cards being produced as fast as USCIS ever does. The initial preliminary green card approval was delayed for a few weeks because the officer needed to check with their supervisor but that only took two weeks.
I wish the OP luck - use the time to get to know each other more, if you're able.