Indicative Vs Subjunctive
 

"Mi hermana mayor no está de acuerdo conmigo. Ella siempre me dice que escuche a mis padres porque no quiere que yo dependa de ella en el futuro. Lo que más me molesta es que ella ‘tenga’ razón."

Can we use the indicative ‘tiene’ instead of ‘tenga’ in the last sentence here (assuming that I think that my sister is always right, every time she gives advice)?

Many thanks.

"Tenga" is necessary because expressing an opinion or a feeling with this kind of structure needs the subjunctive.


- Mi hermana siempre tiene razón y justamente me molesta que siempre tenga razón. ;)
You may say "lo que me molesta es que siempre tiene razón", because the structure introducing another verb ("es") breaks the expression "me molesta que". :)

Many thanks, AngelicaDeAlquezar.
So, my original sentence can be written both ways (with both indicative and subjunctive, and both are correct?
Lo que más me molesta es que ella ‘tiene’ razón.
Lo que más me molesta es que ella ‘tenga’ razón.

Yes.
If I used them, in the first sentence it's been confirmed that she is right, and in the other I "feel in my heart" that she is right, although I don't have a specific situation to prove it.

Thanks so much once again, really appreciate your help!

Glad to be useful. :)