My boyfriend's mother helped me find a job and introduce me to it. How can I send a message to thank her?

I don't know the result yet, so I suggest you don't send a text message to express anything

otherwise it may make your boyfriend's mother feel pressure

It's better to send a text message to express your gratitude after knowing the result

No matter whether it works or not, it's more reasonable

I think it's better to treat her with a normal heart now

Just send some heartfelt messages about her.