technically you will never find one...
the reason as such,
1) lay is some one that never taking the ordination vow only the refuge vows
2) lama is someone that had taken ordination and taken the 3 yrs retreat and judge by his own teacher that he is qualify to teach, so granting the title lama, without they are known as venerable.
so, 1 and 2 already cannot match...
Unless you asking for any lay female teacher that teaching buddhism in sg.. Then I beleive there is...