My preference is "she's looking pretty as always" though I'd accept both sentences. To me, "as usual" isn't as positive-sounding. It's as though her prettiness is common and expected. No pleasant surprises there. "As always" is more emphatic.

Hi! Both sound perfectly acceptable to my ears. However, I prefer "She's pretty as always" as it is more affirmative. I also believe it to be more common.

Hi, My answer is that: She always looks pretty as usual. Then,both always and usual are in the sentence now.

Hi,Shumaila! I think both are ok. Though "always" is different from "usual" both in word class and meaning, "as always" and "as usual" have the same meaning, both mean as was common, so they are subsitutable.E.g. 1. As always he was late and had to run to catch the bus. 2.You're late, as usual.