I would ask if she's using a new needle or the correct needle for the fabric. Is the thread looping or something else? Does she know what kind of fabric she has? She could check with the fabric store. She could try to sew the fabrics and use adding machine paper as a base under the fabric for stability. The best thing would be to get some washaway stabilizer if it can be ironed to the fabric. She may need to change the type of thread she is using as well. What are the two fabrics being sewn together? Are they the same type of fabric? She should check the manual and also the machine's brand's website for tension issues. The site may have a forum where she could ask additional questions regarding her problem situation and get some suggestions or advice.
That's about all I can think of at the moment.
Pam M