are you using the same thread, top and bottom? Also your needle needs to fit your thread (check out Superior Threads for explanation) Change your needle (I use 90/14), then sew a straight line.....if the tension is OK, don't mess with the settings. If the thread is rough the larger eye of a topstitch 90/14 might handle it. Otherwise, I would order the closest match from Superior and have a chat with your friend.

I FMQ everything with Metro machine embroidery thread, haven't had any problems. Machine embroidery thread is usually Very fine and smooth.

Glide or isacord thread has colors very close to that and sews and works very well in FMQ.

Since you know this lady and she has seen your work in the past, just show her the results you are getting with this thread and then ask her again if you can change threads to another type. If worse comes to worst, she can be encouraged to look for another quilter.

I often try a Denim needle when I have problems. I have a lot of longarm friends who love the Glide thread. I have never used it myself.

I like Glide thread to , I would not use embroidery thread to quilt a quilt .
I also like Omni thread ..

I quilt with all types of thread because I love colors more than a brand of thread and in my limited quilting experience I have learned that not all threads require the same tension on your machine. Get out the quilt sandwich and try various tensions with this thread.

Glide is an embroidery thread! Like most 40 wt trilobal poly threads it is quite suitable for both embroidery and quilting. So you are using an embroidery thread to quilt if you use Glide. Filtec started marketing Glide to quilters when LA quilters started recommending it among themselves. They got their big break into the quilting circles when Karen McTavish started endorsing their thread around 9 or 10 years ago. Word quickly spread. But the thread was originally made for the embroidery market as a stronger and more colorfast alternative to rayon. It didn't take long for a lot of other embroidery thread manufacturers to follow suit and start marketing to quilters.
Many machine embroidery threads are made of Rayon. It is the Rayon threads that should not be used for quilting as it is notoriously weak and not always colorfast.