- Early in the film, Amber tell her ex-husband that she has a lawyer to gain custody of her son. When she appears at the custody hearing, she doesn't have a lawyer. Why wouldn't she get one? She would presumably have plenty of money from her films, or has she snorted it all up her nose? Jack has plenty of money too, but does he not support Amber's case, or has she not told him about it? Or is Amber really that irresponsible a person that she can't even organise professional counsel for a case which is very important to her?
- Probably a mixture of all of them. It's pretty clearly suggested throughout the film that while the case is important to Amber and (on some level at least) she genuinely wants to be a good mother to her daughter, she's just not mature and responsible enough to sufficiently get her crap together to make it happen. She's not exactly Ms. Responsible when it comes to life decisions, she's a pretty big cokehead at that point (which isn't going to help re: responsibility), and she and Jack probably aren't making the kind of money they were making in the late '70s when the good times were rolling, so she might not be able to afford a good lawyer. She implicitly loses the custody hearing, after all (if the fact that she's seen afterwards sobbing is any indication), so there were presumably reasons for it.
- She could also be simply lying about having retained a lawyer in an attempt to get him to back down, and he called her bluff.
Headscratchers / Boogie Nights