I am getting old and I vote for a magnetic interlocking clasp rather than being dependent on someone else. She can do it herself.
If you have the box and/or the miki clasp, and any paperwork keep them and when she is done with the necklace, restring it back if it is to be sold.
Sterling interlocking clasp $6.99 at Artbeads no postage. fast delivery:
http://www.artbeads.com/iscl-0028.html This clasp will not come undone by pulling or yanking, you have to break it open. It has ridges which prevent it from coming apart when yanked. I wear them everyday. Just make sure the magnets are in there tight. If not a drop of superglue is a good idea. That is the only problem with those clasps- the magnets some times come unglued. They usually don't get lost because they are stuck on the other magnet.......
I have a pacepaker and it is ok with this klind of clasp- I asked the company that makes the pacemakers amd was told that it is no longer a problem. So even though the artbeads magnetic clasps have a pacemaker warning, it is not necessary for that strength magnet.