A few things that come to mind:
1. We don't know if it's a credit card or a bank card that was used, right? In any case, the new chip-reader things that you just tap your card onto, don't even require a password or PIN. It's quite possible that they had her wallet and used it without needing to transfer funds.
2. There's been no mention of being in possession of anything other than the car and the bank/credit card, right? Nothing about a wallet? (even in a "theft-under" charge?). Does this mean they just took the card, or ditched the wallet?
3. Where are the parents of either of the accused? I have seen mentions of cousins here and there, but no reply from a parent of either or any other family member? Just curious what they would say or do in response.
4. If you read VL's facebook profile, those posts do not seem to be the posts of someone who could commit murder. They do, however, seem like the posts of a young woman who has gotten mixed up with people/circumstances that she later regrets, (on a regular basis, it seems). At the start of the New Year for the last couple of new years she posts a resolution to make it a better year, go to the gym, etc. etc. This leads me to think that she gets influenced by those around her, when at her core, she isn't "evil". This then makes me think that she, when removed from the person who influences her, might do the "right thing" and cooperate.
All of this is JMO.