All right, if you insist on doing this again this month...
No, we do not "miss" words. We either omit them or rework them so the information is there, even if it's not in the same exact form as the original.
Yes, if you literally translate the text it becomes "I'm with Sumire-chan and everyone else (my other friend(s))"
The problem is that we don't know who the other friend is, or perhaps if there are others off-screen, we don't know if the word "friend" should be plural.
Although the latter interpretation is not super likely, so it's best to assume that the only other friend is the one that we can actually see.
In English, you don't mention one single name. You either say "My friends (and where they are from)", or in smaller numbers,
you mention everyone's name, except because we don't know the name of the other friend, we can't say "I'm with Sumire-chan and XXX-chan."
The fact that this specific character is at the beach is not important information, the important information is wrapped in the fact that they
are her friends.
Are you going to point out every bit of text we "miss" every month? This is starting to feel like harassment, honestly.