Some people are takers and not givers. She takes whatever attention she can, but she will not give others her attention. There are many people out there like that. Do not take it personally, try to see it as she's not getting the attention she wants, so she'll say something mean so the attention is back on her.

I would be like the other guests and ignore her. To say something snarky or to even mention it is only giving her the attention she wants and she'll make you look bad on top of it AND the rest of the group will be affected by it and may not want to get together anymore.

I've been in similar situations, she's had her say, now it's your turn to talk about your day, don't feel threatened or discouraged by it. Her mean words have nothing to do with you.