Verified answer

You assumed correctly!

Sé - with the accent is the command or imperative form of the verb SER - to be.

Se - without the accent is a pronoun, it could be a reflexive pronoun, or a direct or indirect object pronoun.

It does throw people off! Accents are important! Like Sí with an accent means yes, while si, without the accent means if.

Buena suerte!

"Sé" is the imperative form of the verb "to be".

"Novia" is a feminine noun so the article is affected -> "una".

"Sé una mejor novia!" sounds perfect for "Be a better girlfriend", yes.

As a reply to the previous comment, "Sé una novia mejor" sounds too awkward to me, and I'm also a native speaker of Spanish. Probably because of where we come from? I don't know. I would say that "..mejor novia" is the most common way of saying it. I'm sure.

It does mean be a better girlfriend, but Google Translate screwed up the grammar they should have said Se UNA novia MEJOR I bolded the corrections to make it clearer.

Hope this helps

Be a better girlfriend