To the best of my knowledge, since .bashrc is in your home directory and the source command is used without an absolute path (i.e. source .aliases), it would expect the .aliases file to be in the home directory. Note that the .bashrc file runs every time you open a new terminal instance.
That being said, I haven’t really tried not having my .aliases and .functions in my home directory, so I’m not sure. If you try this out, lemme know!