Having three companions at once isn’t unheard of, but it’s a bit unusual. Sort of makes the Doctor feel like she’s travelling with an entourage, but if she wants to take one with her, she has to take the other two as well. They’re kind of a package deal.
It’s okay though, it’s sort of fun, except when there’s danger and she has to keep an eye on them all at the same time. Three companions, two eyes… It gets complicated. Sometimes she wishes she’d regenerated into a Xantillian instead of a woman; the extra eye would come in handy.