How can I get people to join our facebook group?

[Apollo Rules]

My friend runs a 501c3 non profit animal rescue. She has a facebook group where people can go and share the animals up for adoption and talk about whatever they want pertaining to the animals. Recently a LARGE organization in a local big city started their own group and they have over 500 likes. Theirs is not a group it is a business page but they are giving her so many problems and she just wants to prove that she can continue with her smaller rescue even though they are flooding the market with animals they are buying rather than rescuing. Is there a way I can post somewhere asking people to join the group and to share the stories of the animals available for adoption? She is not asking for money. She is asking for people to share so that she can find homes for the animals. Any help would be appreciated.

This is the group

http://www.facebook.com/groups/337127503037878/

[Patrick Harrison]

Its simple, pls follow the following steps to do it:
1. Join a Group on Facebook, which you like the most, which is related to your liking, and regarding which you are aware of and do have a basic knowledge.
2. Select the people there on the Group, and invite them to join your friends network (donot forget to include a short welcome message in your request, and let them know that you are connected with them throught the Group).
3. Send them the message by selecting Group members, one after another.
Then see the wonders happening.