Are 'a rumor,' 'the worst part,' and 'merely kept quiet' correctly used in the sentences?

RommelOnce there was a rumor about my girlfriend having a romantic relationship with another man. The worst part was that her peers spread it. I actually believed it, even though I merely kept quiet.

All the sentences are fine except for the third one. It doesn't make much sense to me. You "kept quiet" about what? To keep quiet about something means that you d

XerxesYou "kept quiet" about what?

Would it be correct, then, if I wrote as follows?

Once there was a rumor about my girlfriend having a romantic relationship with another man. The worst part was that her peers spread it. I actually believed it, even though I merely kept quiet about it.

'It' refers to the 'rumor.'

XerxesEveryone knew that my girlfriend was cheating on me, but everyone kept quiet to spare my feelings.

In this sentence, 'everyone' is mentioned twice. Is there any other word that can be used instead?

RommelIn this sentence, 'everyone' is mentioned twice. Is there any other word that can be used instead?

There are other words that can be used instead and, in fact, the sentence can be restructured any way you want. I was only using this as an example to show you how to use "keep quiet".

Would it be okay to say He kept quiet on the rumor? I notice that many natives use the preposition 'on' which has the same function as 'about.'

"On" doesn't sound natural to me.

He kept quiet about the rumor.

Thank you, Xerxes, for helping me choose the correct preposition.