No, sleeping on a hard surface while breastfeeding is not only perfectly safe but very pleasant for the mother. I have done it with three children and most of the world has done it for most of its children for most of its history. Place the baby in such a position that it would not fall off the bed.

There are some exceptions to this rule that have to do with the mother being heavily drugged or intoxicated, but given that OP posts perfectly coherent messages without any lapses of reasoning, I would say that she is clearly not abusing drugs or alcohol.

I have not checked these guidelines in more than a decade, but back then, many years ago, the world health organization recommended breastfeeding until at least 2, and american pediatrics society (approximate title), until at least 1. I very much doubt that since then, those guidelines have been changed to reduce the recommended duration of nursing.

Sincee nursing is also beneficial to the mother's long term health, there should be reasons to stop it that are strong enough. Say, if the mother absolutely must take a medication that is incompatible with breastfeeding.

Feeling a little isolated is not such a reason. It is a problem that should be solved using tools that are more peaceful and less harmful than early weaning. Jogging stroller, new moms group, yoga,sex, etc.