There are some great online dating websites that your mother can meet great guys that are or were in her same position. You can check out match.com or harmony.com. They are two of the more popular sites.
I might also suggest having your mother sign up for some local activities through the local community center. That is also another great way to meet people in your community who enjoy some of the things she enjoys.
Whatever you do, don't put more pressure on her to find someone. That will only make it harder and more discouraging for her. Try to be supportive in any way you can and be a good listening ear. There will always be men out there who are going to break hearts, but when she finds the right one, it will all be worth it. Just be prepared to be a good shoulder and/or ear for the bad times.