Can daily Mass fulfill the Sunday obligation for someone who is ill?

My sister will only attend weekday Masses. She served as a military nurse for 20 years and suffers PTSD from three tours; two in Afghanistan and one in Iraq. When she is in an environment of many people in a confined space then her PTSD is very heightened, such as a large parish. She lives in an area where all parishes there have a great abundance of Sunday faithful. Therefore, she goes to the sparsely attended weekday Masses and volunteers at the church.

Some say she is in mortal sin for not going on Sundays. Is she? Or can the weekday Masses fulfill her Sunday obligation? The pastor of her parish has told her it was okay for her under the circumstances. He has said because it does fufill the Sunday obligation, she does not require the Eucharist at home via an EMHC on Sundays. However, the military chaplain, who also knows the circumstance, has told her it is mortal sin.

There are several points to be made here.
*]No, weekday Masses do not fulfill the Sunday obligation.
*]However, those who cannot attend a Sunday Mass due to a medical condition are not obliged to go.
*]Even though the weekday Mass does not fulfill the Sunday obligation, your sister does not require an EMHC to visit her on Sundays. She does not have to receive Communion on Sunday, as the obligation is to attend Mass and not to receive Communion. She can receive Communion at the daily Masses she attends.
*]Mortal sin requires grave matter, full knowledge, and deliberate consent. All three elements must be present for there to be mortal sin. As not attending Mass on a Sunday or holy day when there is just reason not to do so is not grave matter, that element is missing in this circumstance.
*]Your sister really needs to stop “shopping around” for answers to this question. Doing so is only going to disturb her spiritual peace. If her pastor is telling her there is no sin involved, then she should accept his judgment and let the matter go.
*]You need to stop worrying about this situation as well, if only to avoid heightening your sister’s anxiety over her practice of her faith.

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