if it's a first-time ewe, then persevere with the supported feeding. Very good chance she will settle and become a good mum from hereon.
I have had them take a week, even 10 days once, but it's usually more like 2-4 days, often only a few feeds.
My feeling is that these new sensations can take some getting used to!
If it's an experienced ewe then there may be something else going on, but I would still do the supported feeds and hopefully she will settle. They say that after a week, the lamb smells of the ewe, and she will take it then. But the issue here seems to be that she loves it, just doesn't want it to suckle.
On techniques for restraining the ewe while the lamb feeds, I found that the lighter your touch and the less of a fight it is, the sooner the ewe will come around. So my usual technique is to quietly pin the ewe against the wall of the pen, with her nose into a corner, using my legs at her shoulder and hip, with one hand gently but firmly supporting her chin and the other pressing on the spine as shep53 describes if necessary. The lamb will get it and come diving under after a couple of feeds. Relax the pressure as much as and as soon as you feel you are able so that the ewe feels less constrained as far as possible consistent with getting the lamb fed safely.
And there is nothing wrong with giving the ewe some cake to keep her occupied while the lamb is feeding