dāngrán, nǐ xiànzài dǎ diànhuà gěi tā, huòzhě wǒ lái gàosu tā, dōu kěyǐ.

给 marks the recipient (to/for). Both orders are correct:

• 给她打电话 (Mainland-preferred)
• 打电话给她 (very common in Taiwan; also understood in the Mainland)

They mean the same. A very common colloquial variant is 给她打个电话. Avoid forms like 打给她电话 (wrong).

General rule: 或者 is for statements; 还是 is for questions. But when you add 都 to mean “whether A or B, it’s fine,” both can work:

• 你现在给她打电话，或者/还是我来告诉她，都可以。 With 都, 还是 no longer forms a question; it reads as “whether A or B.”

Here 来 is a light verb meaning “I’ll take it on / let me do it,” not physical motion.

• 我来告诉她 = “Let me tell her / I’ll handle telling her.”
• 我告诉她 = neutral “I’ll tell her.”
• 让我告诉她 = “Please allow me to tell her” (asking permission).
• 我去告诉她 = “I’ll go (there) and tell her,” focusing on going.

No measure word is needed if you just mean “make a call” in general. Use a measure when you mean one call:

• 给她打个电话 / 打一个电话 (colloquial, very common in the Mainland)
• 打一通电话 (also common; especially frequent in Taiwan) Note: 打通电话 means “to get through (successfully connect),” not “make one call.”

当然 adds reassurance/affirmation (“of course”). It’s optional. You can also say:

• 当然可以。你现在给她打电话，或者我来告诉她，都可以。 Sentence-final particles like 啊/啦 can soften it: 当然啦…

Time adverbs usually go after the subject and before the verb phrase:

• 你现在打电话给她… You can also front it for emphasis:
• 现在你打电话给她… Putting it at the very end (…你打电话给她现在) sounds unnatural.

Yes:

• 要么你现在给她打电话，要么我来告诉她，都可以。
• 无论你现在给她打电话，还是我来告诉她，都可以。
• 不管你现在给她打电话还是我来告诉她，都行。
• 你现在给她打电话也行，我来告诉她也行。

In speech, context decides. In writing:

• 她 = she/her (female person)
• 他 = he/him (male person; also generic “someone” in some contexts)
• 它 = it (objects/animals) Here 她 makes it clear the recipient is female.