Q: My wife had menses for nine days. A week later it continued again, should she ignore it and pray or should she consider this as menses also and stay away from salah?
A: In the case you mentioned, your wife should do the following:
1) If she has a previous, known cycle, for example, 7 days or 8 days, etc. then she must regard her Haidh as that number of days. In other words, she must go back to her previous cycle. The other days will all be Istihaadhah, meaning that she can make Salaah and fast, etc but she must make Wudhu for every Salaah.
2) If she does not have a previous cycle, or she cannot remember her cycle, then she must consider her Haidh as full ten days, and the rest of the days as Istihaadhah. She will make a fresh Wudhu for every Salaah. If there is bleeding then she will have to change pad, underwear etc before the Salaah so that when she enters Salaah, she is clean.
3) Remember that she has to have a bath after the ten days have ended.
I trust you understand my answer. If not, please feel free to write back