Ah, more jumping to conclusions using incomplete data. NEVER a good idea. Especially using Ancestry's data. Upload both your and your mother's results to FTDNA ($39) and GedMatch (basic service free) Convince your possible cousin matches to do the same. Then and only then you can come to some accurate conclusions.

After you upload to GedMatch, use their "Are your parents related" utility to see if a match could come from either side since there are common ancestors.