There have previously been posts about how to let the bot allow other people to get into your party and have the bot run it's functions.
However... The bot will not follow a manual player in any scenario. The manual player would have to try to follow the bot.
There is a "party" plugin called "Autofollow" available in the plugin section of the forums. This program is meant to connect two demonbuddy bots together. Most people use multiple bots on the same PC so they get the advantages of group play (buffs/experience/etc) without the need for other people. It is relatively easy to setup AutoFollow in a way to connect bots on different computers or over the internet. But again, both have to be using demonbuddy...
The bot will only follow another bot due to the way player information is gathered by AutoFollow from DemonBuddy. As far as I am aware, AutoFollow works by one bot sending it's location and other information directly to another bot. This [educated guess] bypasses the need to grab information directly from the server.
...I don't know how safe it would be for DB to get another players information from the server.
If your main question relates to using the bot in general public servers, you're just asking for a ban. Too many people can easily recognize the way a bot plays vs. a legit player.