Still-A there are many reasons as to why a sister is announced "no longer a regular pioneer"
1. Maybe the sister could not do the required 90+ hours a month and informed her elders.
2. Maybe the sister was "privately reproved" for some wrongdoing and the elders stripped her of her pioneer status.
3. Maybe the sister is dating a non-JW and the elders have talked and talked to her to stop.
4. Maybe the sister was caught "padding" her field service time slip.
I remember years ago when I was a JW an elder in my hall was "removed" as an elder and it all came out that this elder was having an "affair" with another JW but he never was disfellowshipped. He divorced his wife and married his "mistress".
So it could be a number of reasons.