Interjection for a longing sigh

Is there an injection or at least an onomatopoeia for a longing sigh that works in writing? An example would be two colleagues are talking about the new member of the team on which one has a huge crush:

[the word], he/she is soooo cute. I really should make a move.

All the positive interjections I know (oh, wow, phew, gee, awww) don't seem to work... at least for me (not a native speaker of English) To my perception, they are either too surprised, too amazed, to exhausted or too relieved. They are all not longing enough.

• Is there anything or is the only way *sigh *?
• Could I use sigh in spoken English or does it only work in writing?

It's true that when that feeling of longing and desire strikes, words just aren't adequate.

A drawn out mmmmmmmm-Mmmmmmmmm!" should be understood to be an expression of approval (with the emphasis on the 2nd Mmmmmmmm).

OR

A 2-note whistle, like a wolf call but kind of done under one's breath also conveys the same meaning of "oh boy!".

If those suggestions aren't enough, a long, audible inhale followed by an equally long and audible exhale have the same meaning - if performed as part of the same interaction with the friend and the object of desire.