1. The property owned by the father of your mother devolved equally on all his children after his demise. As such, your mother's share in the property is 1/9th.
2. The will that was fraudulently got made by your maternal uncle can be challenged by you on the ground that it is vitiated by undue influence.
3. Once the will is struck down as illegal by the court the property would be partitioned equally among all the legal heirs.
4. In addition to challenging the will, your mother can also file a criminal case for forgery and cheating against her brother in the court, whereupon he may be imprisoned if held guilty.
5. Along with challenging the will your mother is required to seek the partition of the property to cull out her lawful share.
6. As regards the property which has already been sold, your mother can seek apportionment of sale proceeds, or she may challenge the sale itself which created third party rights.
7. I presume the probate has not been granted yet.