Hello
@Annfaye and welcome. When someone first goes into a care home it can be a difficult in terms of helping them to settle in and start to rely on the staff for their care, and also to get used to new surroundings and routines. Sometimes seeing family/friends can act as a 'trigger', a reminder of home which can cause upset or unsettle the person, however there does need to be a careful balancing act to also consider the family/loved ones who also need time to get used to the new situation and may well have concerns about care if they are not able to visit. A three week 'blanket ban' on visits does seem a little harsh but we don't know all of the circumstances.
From experience, care homes tend to prefer a single contact person to discuss care etc with, usually a close family member or someone who holds Lasting Power of Attorney, so will probably be reluctant to provide a neighbour with too much information. It's always better to raise any issues directly with the manager rather than administrators (who may not always give out the right/full information), and hopefully they would be able to explain the exact position and put your neighbour's husband's mind at rest about her care and how she is getting on. Would your neighbour's husband or another close family member be able to call and speak to the manager of the nursing home about their worries and ask about the visiting situation?