That sounds like the crappiest way to learn you have MS ever.
I’m so sorry you’ve heard this from what sounds like the least ‘people friendly’ neurologist in the world. Not that it’s ever a nice thing to hear, but actually you want, or need, more than that.
You should be assigned an MS nurse, who may have a bit more time to help you get your head around it. If you’ve not been given the contact details of a nurse, try phoning the secretary of the neurologist and ask for them. Otherwise (and it might be a good thing to do this anyway) make an appointment with your GP to talk about your diagnosis and to ask her/him about an MS nurse. Any questions you have about symptoms and potential relapses could be talked over with him/her.
Meanwhile, have a look at https://www.mstrust.org.uk/understanding-ms/newly-diagnosed-multiple-sclerosis There should be some useful information to help you to understand the diagnosis.
You should also be given a choice of disease modifying drugs to help reduce the number and severity of relapses. This might be what the January appointment is for. Your MS nurse will be a useful resource to talk through your options, meanwhile, here a guide to the DMDs available for relapsing remitting MS: https://www.mstrust.org.uk/understanding-ms/ms-symptoms-and-treatments/ms-decisions Chances are you won’t get a completely free choice of all the drugs, it will depend on what prescribing criteria you fulfill plus what drugs are actually possible in your local area.
I suggest that you also check that the neurologist you saw is an MS specialist. Have a look at the consultants on your hospitals website, it will tell you the specialisms of the various consultants. If there’s another neurologist who is a specialist, try to see if you can switch to them. Have a talk with your GP about what the consultant was like and see what they suggest.
Feel free to come back here and ask us questions, someone is bound to have experienced whatever you are going through.
But don’t expect to get an MS diagnosis and to be able to just handle it. It’s a big thing for you, your partner and your family. This could be why your partners mother is being a bit odd. She’s maybe wondering how this will affect everybody. I know this isn’t helpful to you, but it’s also understandable.