We don't know the details....but, lets just say that he "knew" that the deceased woman's daughter was a lesbian....and here she is before him, with her partner....and approaches for communion. Is he just supposed to give it to her?
This is just another reason to have people go to Holy Confession before going to Holy Communion. It would have given the priest a chance to "council her in private".
This way the priest also knows who is who, and who is approaching the Holy Gifts.
My parish tradition is we Confess prior to going to Holy Communion. This way when our priest notices an "unknown" face approaching, he quietly speaks to them, lifts the chalice for them to kiss, and has them move on. Nobody except the person immediately behind them realizes the person didn't receive the Holy Gifts.
I went to an RC funeral last year (coworkers family member)....and for their Communion most of my coworkers went up too. I know some are Catholic...but, then there was this one Baptist man...who happily went up and with a smirk on his face coming back up the aisle munching on the wafer...with a huge grin. "Good cookie".
I know that priest didn't know who these people were. But, he did in fact, give the Holy Gifts to a "non-believer". This man thought it was all a joke. While not RC, it still hurt me to see it happen.
So, I believe the priest has every right to withhold Communion. It's his responsibility to safeguard the Gifts.