what is insu?

Hello everyone, I saw this word or particle twice in two situations but I don't know what it means

For example:
Person 1 sees something cool

Person 1: めちゃかっこいい！

Person 2: ですよね！めちゃかっこいいんすよ

I don't understand the "んす" part and I can't find an explanation for it.

Example 2, a girl hasn't been on instagram in a long time

Girl: いんすた久々投稿。

I'm not sure if it is the same here but I need help.

1. you're not parsing your hiragana properly
2. "insuta" is short for instagram.

But in #1 that was the exact conversation, Person 2 was probably using slang or informal writing.

insu is not a separate word or particle.

then what is it?

めちゃ かっこいいんすよ is a somewhat sloppy, slang way to say:
めちゃ かっこいいんですよ.
In. Textbook style Japanese, it is
めちゃ かっこいいのですよ。

so she was looking for an explanation of why Person 1 said "mecha kakkoii"

so she was looking for an explanation of why Person 1 said "mecha kakkoii"

what made you reach that conclusion?
she was emphatically agreeing with person 1.

http://www.guidetojapanese.org/learn/complete/explanation

This is what made me make that conclusion

the preceding ですよね！should have made it clear that that was not the case.

so, what does the "no" mean in the sentence?

You must get rid of the idea that for any linguistic construct you encounter, it is always possible to definitely say that it means this or that. And, by the way, it would also be nice if you gave more details about where your material comes from. If it's from an everyday conversation or other non-authoritative source, remember that Japanese people, like everybody else, also make mistakes in their own language.

In this case, I'd bet that this usage of the no+copula construct would normally be considered ungrammatical, and the speaker's intention (if there is any at all) was probably just to add some emphasis, or simply to sound cute.

"めちゃかっこいいんすよ" is a colloquialism that's been around for at least a few years; in english it might translate to something like "hella cute"