Bellatrix is a dreadful hostess, but she actually made an effort. She mingled with all of the guests, but spent most of the afternoon staying fairly close to Narcissa. She was wearing a set of scarlet dress robes and her gift was a ridiculously extravagant sapphire, pearl and diamond choker because her baby sister is getting married and she doesn't do wedding-type gifts.
And then at the end of the shower, she gave Narcissa a hug, kissed her cheek, said she had matters to attend to but if anyone should ask she was, of course, still at the house and then took off before her sister could kill her.