So where is the other code? Who owns the computers? Is it deployed anywhere?
I'm having trouble understanding what could motivate someone to behave so bizarrely. Has she lost the code, but doesn't want to admit that it's just barely running in prod?
Pretty insane situation! I can only guess that she is hiding something. Some possibilities, maybe: She lost the code and can't access it, but it's till running in prod; She hired someone else to write the code and doesn't want to be exposed as a fraud; She has some personal history or a contract dispute with Max that you are not aware of.
Regardless of her motivation, it seems your priority should be getting access to whatever code or binaries you can, and quickly. You mentioned the code is on AWS. What's protecting it there? Can you SSH into the box? Is she holding the AWS account hostage? Even if you do get in, can you extract the code from the server? What's the architecture/language?
Sounds like an amusing situation anyway, I hope you're at least getting paid well.
If the code is on AWS, try to get access to it from there. If it's perl/python then you will have the scripts. For others you can try decompiling the code as a last resort.
In your contract do you have a clause that she has to share the code? If so tell her point blank that she has to share the code otherwise she is in breach of contract.
If she says that she has already shared the code, look for specific functionality in the product and ask for the code that corresponds to that function/action.
I'm having trouble understanding what could motivate someone to behave so bizarrely. Has she lost the code, but doesn't want to admit that it's just barely running in prod?