BJJ people and experienced martial artists! HELP! How can I convince my mum?

Ask her to try it with you that way you'll insure you have a female sparring partner and tell her she can't say something bad about something she doesn't understand until she has tried to understand it a bit, step one plead your case to the instructor, step two have the instructor and your mom work out some sort of agreement where by he leaves the rest of the cl alone for a bit and gives a private lesson to you and your mom on the finer points of BJJ and she will see that although it looks quite gay(it does but so do lots of sports eg Am football,wrestling,rugby figure skating ,etc. ahem anyway)it is a legitimate sport and form of self defence,here are some other points if your mom goes in as a beginner and you do then you'll both be on the same level won't you? if she is really concerned for your safety she'll give it a go