Everyone has a different combination of needle and thread that works for them. And each has their pros and cons.
You should try what she suggests, but also try others, so that you can decide what you are most comfortable with.
I use a number 11 applique needle and Mettlers 60wt cotton thread
A very thin needles really helps to make the invisable blind stitch but the straw needle is too long for me to be comfotable to sew and to get the accuracy that I want. But, I know many who are more comfortable with the straw needle than the shorter applique needle.
The silk thread must be knotted on the end of the needle to prevent it from slipping off all the time. I dont enjoy sewing with the silk thread, but others swear by it as you only need one or two colors for all your applique.