I think you will get a variety of responses to your question, most of which are based on opinion not legal grounds.
If you search on recent threads you will see what I mean.
Things for your friend to consider:
1. SXM timeshares are subject to SXM laws not US laws, regardless of who owns the property or where they are based.
2. The wording on the original timeshare agreement is important. That needs to be reviewed before any action is taken.
3. Even if a Credit Rating is effected, is that preferable to ongoing maintenance fees? Most companies will ask additional questions if your credit report has only 1 negative listing.
4. The timeshare week # will effect how easily the week can be resold or rented by the resort. That could make a walk away easier for all parties.
Hope these thoughts are helpful.