In my opinion you are going to need to add a new member (sorry).
The two main options that are suggested to beat charlotte are trick room or changing her field. If you are going for trick room approach, heatproof bronzong is the way to go and it can be partnered with the gigalith from 7th street to sweep. If you want to change the field, you can find numerous blizzard users in celestine mountain.
Best of luck with charlotte, she is the toughest.