How to handle a lawsuit threat?

[Julia LaVigne]

Hi there! New landlord here and looking for some advice!

Details: Louisiana property. I inherited a tenant when I bought the property. I did not renew a lease with the tenant. She immediately began threatening to sue if I did not give her back her full deposit. I kept out about $500 of $1700 for the maintenance she was required to do in the lease and did not. A few weeks after receiving her itemized deduction and remainder of deposit, she sent an email to dispute charges and threaten lawsuit again. I did not respond since the disputes weren't legitimate. About a month after that initial email (last week), she called and emailed again disputing charges, threatening to sue, and asking for our energy bills to audit us (one meter was split between two units and payments based on percentage agreed upon by past landlord). There is also a clause in her lease that all expenses from any legal action she takes against us would be her responsibility.

Questions: 

1. Should I respond or wait for communication from an actual lawyer? 

2. Do I have to give her those energy bills without some kind of court order (to be clear the bills were split according to the agreement, nothing to hide)? 

3. Is the clause in that lease requiring her to pay our expenses resulting from a suit legal? If so, should I be seeking a lawyer to handle this/possibly prepare a countersuit?

Thanks so much for any advice you have!