Hi Danni, welcome.
We had that same type of marking talk several years ago regarding a sister that married an unbeliever. As you stated its pretty much to make an example of your friend and let everyone else no that that's a no no. If they were to ever get married, the gossip should die down and things should level out as far as them being viewed as any other JW with an unbelieving mate.
I see what you are saying about the hypocrisy, they say they are doing the marking to prevent the "erroring one" from being a danger to the congregation but its not like they are going around trying to get others to marry out side the truth in the first place. Besides, the marking talk is most likely the first time many in tge congregation are being made aware of the person's situation. That was when I found out about the sister in our congregation.