Assalamu'alaikum sis!
I know a couple of sisters who've been through that same path you're about to journey upon. I have friend who has been a revert for 9 months now and she has yet to inform her parents about it. Her parents are quite old but more importantly they're both ill, so she thought it best not to inform them right there and then. Her parents hold the same views that your mum holds aswell. What she's waiting for is the right moment to tell them, but till then, she's making sure her behaviour and character is beuatified by Islam so that when she does eventually tell them, she'll be asking them whether they've seen her behaviour change for the worse, and thus that Islam teaches respect, honesty and kindness etc.
The best thing to do is probably the same. Most importantly, continue respecting your mum throughout and I guess through the beauty of Islam's teaching, your character and behaviour will change according to Islam's teachings. You're mum will insha'Allah see no difference, rather a better change, and eventually you'll be breaking the misconceptions and stereotypes that she holds. Islam places your Mother at a very high status - Remember, you're the person that will now shape the image your Mum has for Islam. You're actions, your words, your character, the way you interact with people etc all this your Mum will witness, and when you eventually do tell her, you'll be sure that you've given the best possible image of a Muslim - something that will insha'Allah reach your Mother's heart. Be sure to keep her happy at all times.
With regards to the Arabic language, as all have mentioned, you just need to know the basics i.e. Believe that there is no God but Allah, and Muhammad SAW is His servant and Last Messenger and the 5 pillars of Islam. Take it easy with everything else - to this day, people born Muslims still learn more and more about Islam everyday - which is the beauty of it all.
I'd say if you do have an Islamic Society/club or something like that, you could maybe join it, because then you'll meet other sisters who could help you with any questions you may have or just be a good companion to you. Sisterhood is really important in Islam and you'll find that it really helps to have other Muslim sisters around you.
One last crucial point - make constant du'aa to Allah swt! Du'aa is the weapon of the believer - turn to Allah swt at all times, He's there for you, He hears your prayers, He will answer it iA (in ways which might not be apparent to us at first), and He's the only one that can guide. Turn to Him at all times and ask Him to open your Mother's heart too. May Allah swt answer your prayers.
May Allah swt be with you sis, and make it easy for you! You're in my du'aas.. Have you said the shahadah btw? Try your best not to delay it - no one knows what tomorrow will bring..
And Allah swt knows best. And He reaches to every servant that calls out to Him.
