Responding to a question about whether Arias's lies - which only started AFTER Travis Alexander 'was killed' (note the passive) - represent a problem or issue for LaViolette, she responds "No, because If Miss Arias was a really good liar, she would have planned a really good lie, and she didnt".
Arias didn't plan a really good lie, because she had no notion or conception of the fact she would get caught. When she came under suspicion - as she knew she would - she truly believed she would be able to wriggle out of it with her weak @ssed ' Oh I loevd, loved loved Travis and would never, ever harm him! I was in Utah, and I can prove it - see, these gas recepipts, see this LEO pulled me over for an upside down license plate see, see, see!'.
She didn't come up with a good enough lie because she's a narcissist who thinks she's cleverer than a detective with 25 years experience. She also thinks she's cleverer than you, Ms LaViolette, and at this point I'm thinking she may well be right about that.