SOLVED. YA Sci-Fi Romance. Main character is a female in STEM I think Mathematician, she is working towards some research with colleagues, one of the newer guys is quiet and dresses strange. Spoiler in comment. [s]

[Emily]

(view spoiler)[the strange guy ends up being an alien who is trying to get home, she ends up having a romance with him. (hide spoiler)] Would guess that I read this around 10 years ago so 2010/11 and would have picked up at waterstones.

I think the female lead either had red or curly hair?

[Rainbowheart]

How old is the main character?

This sounds more like NA or adult, not YA.

[Becca]

It sounds like Resistance is Futile by Jenny Colgan, although it was first published in 2015 so a little later than your estimate.

[Emily]

Could possibly be NA but more on the border, of YA NA.
Main character was between 20 and 30

[Rainbowheart]

YA from juvenile publishers means high school age, so this sounds more like adult fiction to me. Especially if the character was post-college and had a career.

Was this primarily a romance?

[Becca]

So is that a 'no' to Resistance Is Futile, or are you still looking into it?

[Emily]

Becca wrote: "So is that a 'no' to Resistance Is Futile, or are you still looking into it?" Hello, Thank you to your response! I'm signed up to email notifications but they've been filtered away!

Yes Resistance is Futile is the book, Lockdown must have added on five years to my estimation. Thank you for your help!