Everyone's probably tired of me making this recommendation, but take a look at the Ebonite Cycone.  It's an awesome ball for the price, has the coverstock from The One from about 5 years ago and a strong symmetric core.  We sell them for $102.95 + tax, drilled but not including slug or grips.  --  JohnP 

Without seeing how your girlfriend bowls, it is difficult to suggest a ball.  When I hear 43ft medium oil, it tells me a stronger ball is most likely better with her being a stroker with moderate speed.  I would be weary of encountering enough friction from a pearl to be beneficial.  I have seen the Cyclone used by many and agree it is one of the best deals in bowling right now.  But if your girlfriend is a somewhat competitive bowler and not a true beginner, I would lean toward a higher performance ball.  Not saying a Cyclone can't be high performance; just depends on the bowler and what they are trying to accomplish.

Perhaps the lower RG (than the Signals) Vital Energy or better yet, lower RG Warning Sign with a hybrid cover.  And there is also the new mid-price Elevate with a hybrid cover.  A hybrid cover usually allows an earlier roll than a pearl allowing her stroker style a chance to pick some roll on a bit of a longer house pattern.

If the wood lanes make the medium house pattern dry up real fast, then a pearl like the Signals would be a good choice and possible the Cyclone also could be a good choice. 

It is just hard to suggest without seeing how her Complete NV performs for her on the shot she will be bowling on.