How do people who believe in immediate heaven for believers at death explain Tabitha? In Acts 9:36-41 is the story of Tabitha (a.k.a. Dorcas) who died and was raised to life through the prayer of Peter.  

That would seem to conflict with a commonly held view among theologically conservative Protestants that once a believer dies, that person is in heaven and never returns to this life.

My question asks how that theological view is harmonized with the Tabitha story.  (Is Tabitha the exception that proves the rule?  Is heaven as a one-way ticket only true after the period of the apostolic age, with its miracles?  And wouldn't she have been mighty upset to be called back to earth?)

Please note: I am aware of (and not seeking) alternative explanations as to what really happened when Tabitha died; only want to know know how "immediately-in-heaven" partisans square that view with her experience.
Conservative Protestants typically use the phrase "intermediate state" when talking theologically about the "immediately-in-heaven" view.  Wayne Grudem is a conservative Protestant representative of this view.  In his book, Bible Doctrine, on page 352, Grudem writes,  

"The souls of believers go immediately into God's presence.  Death is a temporary cessation of bodily life and a separation of the soul from the body.  Once a believer has died, though his physical body remains on earth and is buried, at the moment of death his soul (or spirit) goes immediately into the presence of God with rejoicing."

Grudem mentions 2 Corinthians 5:8, Philippians 1:23, and Luke 23:43 in support of this view.  However, he offers no suggestion of exactly what is happening in the case of a miracle when a person is raised from the dead.

From the theologically conservative Protestant position, Tabitha and others like her pose no problem, because the view does not necessarily state that once a believer dies, that person... never returns to life again.  Rather, that is the normal occurrence for both believers and non-believers.  But, God may choose according to His pleasure and mercy, to allow the miraculous to intrude into the ordinary and raise/resuscitate a dead person, again whether believer or non-believer.  That's what makes it a miracle, whether the human agent is Peter praying or a doctor reviving the one who is clinically dead.  Note that this is not merely relying on a miracle to get out of a theological issue.  Rather, the question assumes that miracles do occur.

For the person so raised, what has been his or her experience?  Alas, the Bible is silent on that question.  We do know that the unmerciful rich man suffered apparently as soon as he died (Luke 16:19-31) and returning was denied him.  The Apostle Paul may have actually died in Acts 14:19 and some have speculated that may have been the experience he refers to in 2 Corinthians 12:1-4. Admittedly, that connection is speculative, but if so then Paul experienced the intermediate state and returned. 

When reading of an after-death-return-to-life experience, it's best not to put too much stock in it, but whether believer or unbeliever, there is nothing about the intermediate state that prevents a miraculous return to life after dying.