Hello,
Whether she goes for conventional braces/ Invisalign, she needs to go for a retainer. But the duration of retainer depends on type of malocclusion ( what kind of problem is present). In few of the cases, permanent/fixed retainer is advised. So, I’ll advise you to post some pictures of her teeth/consult over a video call/ visit an orthodontist.
Next Steps
post some pictures of her teeth/consult over a video call/ visit an orthodontist.