In-laws’ marriage in jeopardy

I’m writing this because it seems so unreal. Unfortunately, there is a breakdown in my in-law’s marriage. And I had no idea this was happening until my MIL brought it to my attention.

My MIL started telling me about it, and here is what’s happening: her niece has been married to a man for almost 3 years. They got married at 18 and 20. And over these last several months they’ve ran into a few issues.

What I know from what my MIL shared: her niece grew up fearing sex, and therefore the couple hasn’t had sex for nearly 3 years. The husband doesn’t seem to be romantic with her, and she grew upset and even bitter towards him for not seeming to want to treat her as though he still was interested in her. And now with a lack of sexual and emotional/romantic intimacy, these two are on the verge of separation or even divorce. The niece is the one wanting this, but not the husband. There’s also been a few male friends who have tried getting her attention, to which she has been very open to (apparently the husband is ok with her male friends.)

Now my MIL wants me to go visit her niece to possibly be a voice of reason to her. She claims that I would be a good person to talk to her, being that we have similar backgrounds (we both have toxic controlling moms and both grew up fearing sex, though I overcame that and am now pregnant with my first), and that I could be seen as a mentor like figure that she looks up to.

My issue is that I don’t want to seem like I’m prying or trying to get involved in a situation that I shouldn’t be involved in to begin with. Basically, I feel like I’m supposed to mind my own business in a way... At the same time, I don’t want to see their marriage fall apart while knowing I could have helped in some way.