If Lillee does have Williams Syndrome (it would need medical records to confirm, but she does look like she does, particularly in the childhood photos we've seen), she would be extremely vulnerable to exploitation. Sufferers are superficially able to function and often quite eloquent and sometimes academically average (though their IQ tends to be on the low side overall), but they don't develop a very strong theory of mind and are extremely gullible and trusting. Most sufferers are unable to live alone because they cannot keep themselves safe in social or societal situations. They are extremely vulnerable to emotional, sexual or financial exploitation and are often victims of crime, and do not learn from their experiences very well.
If that is the case then Lillee is a victim in all this, because she will trust her batshit crazy mom 110%, no matter how ludicrous the things she says. It will be extremely difficult to keep her safe, because her mom will have legal custody (possibly Power of Attorney as well) and be in control of everything she says and does - Lillee will not even realise that she needs help.
That makes this a worse situation than the Venus/Margo one, where Venus was smart enough to learn how badly she was being exploited, and mentally strong enough to break free from her mother. Lillee won't even want to, she won't realise anything is wrong.