Random girl on facebook?

There is a girl on facebook , At first , i follow her profile then liked her photo / status . Later on i send a friend request but not accepted still pending . Then i canceled the friend request . On her birthday , i send PM about happy birthday greeting and she replied , then i started the conversation on PM . She seem replied but in very short words . Not all message she replied . Then i ask her "Would u mind i send you a friend request ? " She replied "Okay" then i send friend request to her then she accepted . Then i continue to message in PM . Most of message she replied and some not . She never like my post / status or anything . I mostly liked her photo / status but i never comment on it . Just two day ago i send a PM to her about her photo she post reccently . Here is the example message content "I like you wearing the hat ! " .
She seen the message but no reply (Seen at X.XXpm) . Her photo got some people commented , she also no reply the comment ! About 1 hour later after i send the PM , she liked my photo of my stuff , this is the 1st time she liked my photo . She seen the message earlier before she liked my photo .

So its already 2 day and no reply .

Okay i have 2 question here :-

1.Its okay if she ignore my message but why she liked my photo ? (I just wondering)

2.Issit okay i PM her Christmas greeting on Christmas day ?

We don't know each other / never met before ! Always i PM her 1st . I started PM her since November until 2 day ago , 1 week PM her once !

I know facebook is dangerous if stranger PM . So i not hoping anyting from here just want to be FB friend only

I am a boy !

So what do you think about this ? Need some advice from girl and boy . Hehe

Thank you for your reading .