I work for a large company in one of their many offices. In our office of ~100 people, we have two separate teams whose tasks somewhat overlap. Team A has more entry-level type jobs and does more of the grunt work, while Team B are more of the big idea-types. Each team is made up of a number of different smaller teams, but both ultimately have one person over them. These two then report to the CEO (who works in a different office). I am on Team A (as is ~75% of the office) along with a woman we'll call "Liz." Liz is married to the leader of Team B.
Liz does almost no work; it's rare to find her at her desk. More commonly she is chatting with other staff, hanging out in the break room, or coming in late/leaving early pretty much as she pleases (not the norm for most of our office and no one else on Team A). She is loud and disruptive, and gets away with doing whatever she wants (or doesn't want) to do.
Previously, before they were married, she was actually Team B Leader's PA (Personal Assistant). Apparently other offices who communicate with us did not like this and HR intervened to split them up. So she's now in the same office, but on Team A, and doing a non-PA job. However, as far as I'm aware she's not qualified to do most of the work she's doing and it seems like no mid-level managers say anything about her behaviour because she's married to the boss. Instead, they've lightened her workload because it takes her so long to get anything done (it literally takes her a week to do what should take 1-2 hours).
So it's a perfect storm: Liz is lazy and unqualified, but is also given very little work to do because the mid-level managers know she's not up to anything important.
Aside from the situation generally seeming unprofessional and annoying, it also directly affects me: Liz and I are on the same immediate team. Of the few tasks she does, my work waits on a couple of them being completed. So, as a result, I'm slowed down by her laziness on a few of my tasks. I can actually do what she does and do it faster, but I'm not sure if it's sensible to bring that idea up with my immediate manager (who is friends with Liz). She also tends to ignore emails sent to her, though speaking to her directly generally is more constructive.
I would love to go to HR, but I think it's probably job suicide. Are there any other steps I can take?