did she cancel before the 30 days?
It does depend what has been agreed in the text communication.
However you can rely upon text messages as the basis of the contract. You don't need signed writing. It is just easier to prove what you allege if you do have it in signed writing.
That said, actually the term you rely on assist them more than you. If you have a contract then they are bound. If they want to cancel otherwise than in the contract that you agree then they are liable for your loss and, in fact, 30 days from the events you may well not be able to find another booking to occupy your services. If your contract allows them to cancel without penalty 30 days before the events then it is in their interests rather than yours that the signed writing is received.
On your specific point though you are entitled to rely upon the text messages.
Can I clarify anything for you?
They can't claim the contract is void.
What they might be able to do is void certain terms unless the text messages speciflcally refer to them but all that would mean is that they had no cancellation rights at all which is clearly not in their interests.
Well, then you can rely on it.
Well, it depends.
If you said they can cancel within 30 days of the event then they can cancel consequence free.
If they did not cancel then you have a claim for the sum of your loss. If this isn't a loss incurred then it should b knocked off.
All the best.