I described the practice in the first reply, if that doesn’t strike you, consider a YouTube search for “jayasaro metta”

As for becoming immune, yes and no. It would not be compassionate to be immune such as closing our front door and keeping her suffering out. Compassion is the willingness to co-suffer with people. However, we can keep our back door open, so it is like wind which blows in, through, and out. The more we hold ourselves open and alert, others’ suffering doesn’t “stick” in us and instead, just remains information about them and their challenges.

Her side is the whirlwind of criticism and needn’t be about you. Your side is wishing she was different than she actually is, which makes you compare her to your dream of what could be if only…. 🙂

With warmth,
Matt