BPDFamily.com

Is a substantial fear of abandonment unique to BPD?
Are there any other conditions that have fear of abandonment to the level found in BPD?
Should anyone with a substantial fear of abandonment get checked out for BPD?
(obviously it is threshold dependent - I'm talking about the fear of abandonment to the level as described in BPD which produces many counter-productive behaviours)   

It likely won't matter to the court whether she's BPD or not, or something else that exhibits a fear of abandonment because courts don't like to stigmatize mental illness, especially in family law. If it appears you are weaponizing mental illness be prepared for a good scolding. Same goes for substance abuse. You get many, many bites at the apple in family law court -- focus more on establishing patterns of behaviors that negatively impact the kids. 

Even if you had a professional dx, you still need an expert witness to explain to the court how BPD or any other mental illness negatively impacts the kids.

Short of a forensic makeup on both parents ordered by the court, very expensive, very intrusive and time consuming, everything else will be considered name calling and frowned upon.

As already noted, a lot of claims are made during a divorce, especially a high conflict one, and courts generally ignore it all unless there are 'substantive' concerns such as child abuse, neglect or endangerment.

A psych eval may identify a PD (personality disorder) but doesn't give a clear indication how parenting or children are impacted.  However, a custody evaluation conducted by a reputable and experienced expert — a lousy evaluation can result in a disastrous evaluation report — is intended to dig deeper into the family dynamic, the parents, the children and what would be recommended to the court for custody and parenting schedules.

Be forewarned that a CE will take months, perhaps a year or more.  And they're not cheap.  Mine was 5 months and nearly $4K.  Fast and quite inexpensive compared to others' experiences.  I had a highly recommended child psychologist.  I only saw the preliminary report but it was solid.  We didn't use the final report but having it helped avoid an even more expensive trial.  (All the professionals were hoping for a settlement.  Having the report looming for court was incentive for my entitled ex to finally negotiate a decent settlement.)

In my case my ex's lawyer agreed to my lawyer's suggested evaluator.  You may have to be strategically smart in ensuring you get a solid evaluator.  Courts generally like both parents to participate in the selection.  One approach that generally works is that we (the proactive reasonable parents) do research and find a few of the better evaluators and then present that most excellent short list to the other side to make the final pick.  Court ought to see that as fair.  The point is you have to proactively narrow the options so the other side can't slip in biased or inept evaluators.  (By the way, this approach often works well too when trying to get good counselors for the children.)