Why has she started using my last name when talking to me?

Do you know whether or not she likes you? Because that sounds to me like she does.
I used to do that with my first boyfriend... only when talking about something seriouse though, or when I'd be trying to tell him how much I really cared about him. It was like I said his full name to convey the intensity of how much I was trying to get HIM to listen... listen with his heart. as if saying his full name was talking to him more deeply and specifically, than just his first name... I don't know it was wierd. I was weird back then haha. his name was Michael, but I'd usually call him Mike. But when I was trying to be seriouse I'd say Michael. and only a few times did I say his full name... First, middle, and last.
so yeah, I would suggest that maybe she likes you. especially if its a new thing.

She likes you! And your screen name made my day =) I just answered the 'inside jokes' question... so PROMETHEUS ALL THA WAY! <~~~ band joke =D

She most likely likes you. When I talk to my friends about the guy I like I usually use his last name. I am not really sure why, it just happens that way.

I say you gotta have a really cool last name haha either that or she likes you...

haha.. whenever I talk about a guy that I like to my friends I all ways use his whole name. When talking to the guy I like I notice I say his name to him more in casual conversation, but I don't use their whole name a lot.

I think this girl is subtly trying to show you how much she cares about you.

she lkes you duh

She is really into you that's for sure and its a bit corny if you ask me. What do you say?

Jokingly say her full name but put your last name instead of hers. Hope it is better than Julia Gulia (Wedding Singer reference).

I think she really, really likes you.