Employer has stopped paying my tenant

Rent Arrears

Hi Everyone, 

Wondering if anyone has experienced this before. 

My tenant has been in the property for 3 months now. I received the first 2 months' rent fine and I have a deposit also. 

In February the tenant called to say her employer lost a big contract and she doesn't think she will get her wages. She sent me a text message between her and her employer (Which isn't really proof) 

I have been lenient and have not hassled her thinking if this was true she will be stressed. 

Rent was due 18th Feb. She paid half saying her family has helped her out until she knows more from work. 

I haven't heard anything back and it is now getting to the rent date in March. 

I am just wondering as a landlord where I now stand. 

Do I send a formal letter, Do I ask for proof from the employer? 

How long do you wait until you do anything without breaching some tenant rights?

I just do not want to be months down the line without rent. She is still in the 6 months probation period