1) Planning to live in Warsaw city Near Swietokrzyska
1. You will find the suburbs cheaper and nicer. The area you mentioned is one of the most expensive areas in the city. Public transport is clean, fast and cheap, so no need to live very near your work.
2. Groceries and eating out are not expensive in Warsaw.
3. This will certainly keep your expenses down.
Is there any possibility for her to get a job?
Yes, however it helps if she is well qualified/experienced and/or has a skill that is in demand.
Good luck, I hope you enjoy settling in Poland.