I remember having a lot of trouble against her as well with my mono ghost run. I had hacked myself an additional ghastly and sableye though, which really helped. I remember having set a lot of beam attacks on mismagius, which should be useful in serra's field, but I didn't get too much mileage out of that. Breaking the field with a bulldoze on palossand might be the better option. Apart from that, you should be able to get Spiritomb by now, which has infiltrator, to hit through all her aurora veils. That might be a nice addition to the team.
Edit: Oh, and with spriritomb, you can also breed nasty plot on cofagrigus and mismagius. It's really good on both of them.
That's all I can think of off the top of my head.