First a definition of making a friend
The only definition of friend that applies to a bot on Steemit or other web-based service is "a bot that consistently upvotes, likes, or promotes your posts". I do not believe that you can be a friend with a bot in any other way. Since the bot is not a person there is no need for reciprocation. Just a need to manipulate the bot into "liking" you.
Manipulating the bot
In order to get a bot to be your friend, you need to manipulate the bot into promoting your posts. This is best done by figuring out what the bot is looking for and posting based on those criteria. When the bot is selecting posts at random this can be difficult, but through analysis of patterns could be possible. Other bots may look for minnows that post certain types of things. Or the ultimate way to "friend" a bot is to create one.
Creating a bot
The most sure proof way to "friend" a bot is to make the bot. This can be done with some coding skills, an extra email address, and phone number for Steemit. I will not post details on the process, since I don't believe that bots are conducive to the type of environment that Steemit is supposed to be (although I did think about making a bot to upvote and resteem myself for author rewards and others that would likely get high payouts based on statistical analysis of high pay out posts for curation rewards).
In summary
Making a bot friend takes some work to determine what it is that they are looking to promote. Some bots may only promote certain people. In order to have the most friendly bot one needs to make their own.
There is no such thing as making friends with a bot, only manipulating or creating one.