1. The best friend's occasional faces of horror/anxiety/sorrow, plausibly disproportionate to the situation, supporting an idea that something unsaid is going on.
2. The general focus on their intimacy and closeness, whilst "that guy," off-screen, who's the ostensible love-interest, we know almost nothing about other than that he's objectively kind of scummy.
3. The utterly garbled message at the end plausibly being maybe something bittersweet about the two girls, even if we're not quite sure what (but the first line, "if my feelings are conveyed," would in that theoretical context be between the girls, rather than towards the guy, so perhaps something like: "Even if you understood my lesbian feelings, I know you would pretend not to know," for a classic girls-runs-off-with-guy yuri-angst premise).
4. Finally and purely contextually: For those unfamiliar, how common "I'm doing my best to pretend to be in love with the other gender because I can't admit I love my best friend" is as a plot setup in yuri/yaoi, combined with the fact that none of us have any context for the intended audience, nor an English plot summary, to give us hints as to what we're reading and how to interpret it; important especially with something of this short length where we're expected to fill in some blanks.