BF's Ex-wife is histrionic

I thought my BF's ex-wife was fine, up until he and I really got close and started getting serious. His kids like me and my kids like him and we all get along great. We've been together for almost a year now. His ex has recently started to cause problems. Up until now, there wasn't child support paid to her by him. He has always paid for half of things like child care and school supplies/fees, and kids activities, which was what they agreed upon in their divorce. He also has the kids whenever his is off work (quite often since he's a firefighter) so he feeds them dinner after school, coaches their sports teams, etc before returning them to her for the night. So not like he's a deadbeat dad. Anything but.

Ok so ever since she saw that we've gotten close (a weekend trip to Florida about 4 months into our relationship) she has been trying to dig up any info she can on our relationship (jealous much?) and she has now decided that they are going back to mediation so that she can get child support from him. I know she has HDP from what he has told me about her and from what I have observed myself. Seems like she is going after him now because she sees how happy he is with me and she is doing what she knows will get his attention. Is there any way we can just get through this mediation and then be done with her or is it others experience that she is going to keep finding ways of causing unnecessary drama in everyone's life? Any advice on how to deal with a significant other's ex that has HPD would be greatly appreciated. Thanks!