The Bible is the final authority, which EGW states herself. In other words, if you find anything she says to be opposite to what the Bible says, which I don't expect you will find, the Bible is to be the final authority.

The special light given to John which was expressed in the seven thunders was a delineation of events which would transpire under the first and second angels' messages. It was not best for the people to know these things, for their faith must necessarily be tested. In the order of God most wonderful and advanced truths would be proclaimed. The first and second angels' messages were to be proclaimed, but no further light was to be revealed before these messages had done their specific work. This is represented by the Angel standing with one foot on the sea, proclaiming with a most solemn oath that time should be no longer. {1MR 99.3}

How do you know everything she wrote under inspiration agrees with the Bible? What if someone concludes, based on their study of the Bible, she was mistaken on a certain point?...

Committee on Resolutions offered the following
report, which was adopted :—
Whereas, The spirit of prophecy has spoken in regard to
the canvassing work as being an important means of placingthe truth before the people; therefore —
Besolved, That we recommend that the officers of the T.
and M, Society in this Conference, urge such persons as in
their judgment would make it a success, to enter upon the
work of canvassing for such books as " Thoughts on Daniel
and the Revelation," "Great Controversy, Vol. IV.,"
"Marvel of Nations," and other works on our faith.
Whereas, We regard the Signs of the Times as a valuable
agent in teaching the truth; therefore —
Mesolnei, That we recommend a vigorous canvass to extend
its circulation in connection with "Vol. IV." as a
premium.
Resolved, That we recommend all our people to subscribe
for the REVIEW AND HEKALD.

http://www.adventistarchives.org/docs/RH/RH18860622-V63-25__B.pdf#search=%22 spirit of prophecy has spoken %22&view=fit

The Spirit of Prohecy has spoken DEFINITELY on concerning the work of the Review, the Signs of the Times, and the Sentinel, for WHICH THE PROVIDENCE OF GOD into being......
http://www.adventistarchives.org/docs/RH/RH19021028-V79-43__B/index.djvu?djvuopts&page=19

I personally readily understand that if something is properly proven from the Bible and it contradicts what EGW has said, then as she counsels, the Bible is to be taken as the final authority. However, as already stated, from my observations, such actual “contradictions” are rare whereas one will find more “updated truths” which supercede what was “present truth” for her. Yet both views will still be in spiritual harmony, as in the three possible applications to Christ Olivet Discourse (i.e., Present Day (through 70 A.D.) | Church History | Eschatological Age).

Post #130896 - Sister White violently contradicts the so called Bible...
...Our whole Sanctuary Truth is based off that contradiction.
...And remains fundamental to our denominations life.