Where should I orient my thoughts when the feelings are overwhelming?

Hi Brooke,
I am stuck on a feeling that can’t change. In a previous post you said the change is not instant but it will happen if we allow ourselves to feel the feeling.
I have a sister in law, that to be objective has done nothing really bad to me, but we don’t like each other. She triggers something inside me. She has what I can not have and I wish to have. A family, lots of friends, lots of support. I know that it is also related to personalities, I am not the bubbliest, extroverted person. I am determined, strong, but introverted. Everything she says or does bothers me (and she doesn’t know it, but my husband does, and by the way he thinks I am crazy for that).
Anyway, I have tried to apply the model in this circumstances but I am stuck in the feeling. Today this was the model for a specific circumstance that happened this afternoon. For context. I don’t have children.

C: We haven’t done a will
T: I don’t want to leave anything to the daughter of this person.
F: Resentment, angry and guilt
A: Don’t do anything, avoid to do it.
O: Will die without a will (not my problem if I am dead, but my problem if my husband dies first).

Tried to modify the thought, but still go to a similar feeling, tried to find it with love in my heart, but couldn’t.

C: We haven’t done the will.
T: If I want my nieces and nephews to have something, it is only fair she get the half from my husband.
F: Still resentment, not fair, she doesn’t even say hi the 2 times a year we see her. guilt.
A: Still do nothing, or will do it by obligation and to ensure my family gets something.
O: Will still die withou a will. Or it will bother me.

I have considered the option to leave it to a charity that can do better good for other children. The problem is not the will, it is today, but tomorrow I will find something else.

Where should I orient my thoughts. I know it has been very debilitating for me the feelings I have, but the power of the feeling is too overwhelming, I have tried to think a thought more positive each day, but have not improved much. the feeling always ends in resentment, angry and guilt.