T.F.
We are business owners as well.
$400 would not be worth my time other than reporting her in to the BBB.
In our line of business, word of mouth in the industry is enough to know who to allow 30 days, etc. We just had a scare with 1 company owing us $95,000 and they were talking of shutting a plant down. Thank God, they have paid it all but $15,000 so far. It is tough but sometimes you have to take the hit, right it off and keep going.
For $400, is it worth your time, money and effort for small claims court simply to get a judgement on monies you most likely never see?
Because you sent her a notice stating you would go to collections, DO IT. Always follow through on what you say you will do or no one will believe you in the future.
I see you are in Allen.... me too!! Best wishes with your business.