My mother used a piece of wood in the foot pedal to slow the machine when she taught us to sew. My machine has two speeds, which I have used the same way.
Some machines allow you to insert two needles into the shank.
With the machine you have, are you sure it was designed to handle twin needles? Or is there a width setting you are exceeding to allow it to work with them?
Charging your neighbor for breakage sounds like a good idea.

I agree with Peckish, but would consider asking her parents to furnish the needles after explaining why, since you are teaching her a life skill that she will have forever, and not charging anything to do so. Also, if you do not have any twin needles to use, she will adapt to one needle, she can still do designs, just different ones. Adaptability is one of the best gifts you can give a child.

I agree with this! You are doing a wonderful thing for a little girl who can use some support, it sounds like.

Why not introduce her to the zigzag stitch with a regular needle?

so glad you came up with a good solution. I think it's wonderful that you are engaging a youngster in sewing and quilting--they truly are our future! And as a g-parent of 3 that have a hard home situation due to my DIL mental illness and my son's having to work many hours to support them and not living near us, I certainly appreciate that you are reaching out to this girl and provide a refuge for her where reasonable ways to deal with situations are being learned plus kindness and compassion--wish I could hug you!

twin needles have one end that goes up into the shaft where it is tightened. you can't put two needles in there to work. Only the one hole where the shaft goes.

Rather than looking for an adapter of some sort (which I don't think is possible). I think teaching her responsibility & doing things properly is more important. Not to make her feel bad but so she knows there is a right way & a wrong way of sewing & "pedal to the medal" is not the way to go. I congratulate you on passing on your skills to a young girl & there is so much for her to learn but she needs to learn some patience too. I also like the idea of placing something under the foot to prevent her from pressing the foot down so far, kind of like a "speed inhibitor" which could also slow her down. I know my 2 machines have speed control buttons on them but I know that is not a feature on all machines.

I think you have identified the problem, but are having difficulty with the solution. It really isn't an adapter for the needles, it is correcting how she is using them. This will benefit her much more and keep a wonderful relationship growing with student and teacher! Bless you for working with her.

Besides all the other answers, I've thought of one other thing. Twin needles come in different widths(space between the needles), are you sure you're not using a twin needle with too large of a width for that machine? Or a size too small for the fabric being sewn? Either of these can cause a needle to break easily.

Cari

Ooooh, very good point!