The show maybe could have portrayed her as more uncertain whether Elliot was speaking the truth or not. She seemed to really believe him. If she really believes him, it's rather weird that she wouldn't report it. It's a minor point, though.
I found some a Wikipedia article about why Congo is possibly important to WR if we look at the DR Congo of the real world:
https://en.wikipedia.org/wiki/Coltan
Cliffs:
*DR Congo has the largest coltan reserves in the world, estimated at 64% of the global reserve.
*Coltan is mainly used for producing various electronics, including smartphones/computers
*Mining coltan creates various lung diseases for miners
*DR Congo is highly dependant on the mining industry
*Coltan has been used as a plot point before. In Terminator: The Sarah Connor Chronicles, Skynet needs it to create a terminator army.
Likely theories:
*With the digital eCoin becoming the new currency, having control over an input which is necessary in production of smartphones/computers seems like a pretty good position to be in. There could also be a link to crypto mining, but not certain it is likely that Esmail wrote that back in 2014 or earlier when writing the initial script.
*Whatever WR is developping in the mysterious plant is something which will need a lot of coltan in the future, and will allow her to control the world. This could be any type of electronic that has the potential to change the world (AI-related, power generation-related, technology which allows human bodies to be modified with electronics,...)
*WR is developping something that has to do with time travel and this needs a lot of coltan for some reason.
I obviously dislike the third possibility the least
. I think the probability is very low though, Esmail does not seem like the type of guy that would allow something to be introduced so late in the game that literally changes everything about the show.