Attention members: Your chat widget can create a conversation with any member, not just friends. However, the friends tab will still display your friends only. To start a conversation with someone who is not your friend, simply use the chat composition icon as seen below, and you can also search all site members to select the recipient.
There is also a setting on mobile you may be interested in whereby you can control who can message you for a chat. (see below):
Hope this helps!