Unless she is a very shy reserved type of girl this is another great sign she might be interested.
She may also giggle at little things you say even if it is not funny, it is a sign her feelings are heightened around you and she cant maintain her her usual composure around you.
Other signs can include her being jumpy or quiet around you.
Her being quiet around you is because she would rather not speak out and make any silly mistakes in front of you.
When doing something that requires confidence in front of others (e.g doing a presentation) she may sometimes take a glance to see if your around and listening/looking, this is because she cares about what you think of her.
This first sign with anyone is usually when she looks at you, it shows that she is enjoying looking at you and that you have her attention and this goes especially if she has started to this all of a sudden.
If she’s looking at you with dreamy eyes or a seductive look this is a giveaway signs she feels something for you.
Its just as positive when a girl smiles at you, some girls may simply look at you without any kind of emotion.
She will look at you as a way to communicate that you have her interest and that you can approach/talk to her.
On that note girls will walk past you several times and into your personal space as well just to get your attention so they are noticed.
Some other ways she will bring attention to herself are: Dressing more nicely all of a sudden, making her hair look cute, putting on perfume and putting more makeup on.
This is simply her way of looking good for you usually, whether that person is you is something for you to work out.