Many Kim, "As if" is usually followed by an idea that is not true. She did not ask the question when she glanced up. It just seemed like she asked. 1) She glanced up at him as if asking the question. 2) She glanced up at him as if she WERE asking the question...or...as if she HAD asked the question....or as if she WOULD ask the question. Yes, 1) and 2) are essentially the same. However if she actually did ask the question but the observer didn't hear it, for example, then the idea would be probable. She did ask him when she glanced up. It seems to the observe that she probably did. 3) She glanced up at him as if asking the question. 4) She glanced up at him as if she WAS asking the question...or...as if she ASKED the question. 3) and 4) are essentially the same. So using (as if +S+V ) defines whether the condition is either untrue or probable. Using the (as if + v-ing) form can leave some doubt about the meaning, which would then depend upon the context. Is it untrue or is it probable?

"As if" is a compound conjunction. Compound conjunctions are groups of words that behave like conjunctions. "It looks as if it will snow." As if and as though mean the same. They are used to say what a situation seems like. It looks as if/as though it is going to rain. To show that a comparison is unreal, we use a past tense with a present meaning after as if/as though. She looks as if/as though she is rich. (Perhaps she is rich.) She looks as if/as though she was rich. (She is not rich.) In a formal style, were can be used instead of was to show that a comparison is unreal. She looks as if she were rich. Note that we do not use a past perfect for a past unreal comparison. She looked as if she was rich, but she wasn’t. (NOT … as if she had been rich. In an informal style, like is often used instead of as if/as though. This is common in American English. It looks like it is going to rain. I hope this answers your question. I really didn't understand the way you asked it.

You mean: "She glance up at him as if asking a question" .....or..... "She glanced up at him as if she were asking a question." There is no difference between the sentences. Both can be used.