Looking for a book about a girl named martha who plays at her house. if you know the book please respond.

I believe you are talking about Martha's House by Edith Kundhardt 1982...my children love this book too!
there is one for sale on ebay now: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=110228851484&ssPageName=STRK:MEWA:IT&ih=001
Hope this helps!