Well, no disrespect to your mother, but I think the metal lids work better than jam papers. I have horrid memories of cellophane covered jam going slowly moldy in the pantry.
I wash all jars in hottest dishwasher setting, then put in oven on low I put all lids and seals into a saucepan of water and boil for 5 minutes. When the jam is in the jars, I fish the lids out of the water as soon as they are cool enough to handle.
I have just moved house and on the third day made 'miracle jam' from the Mirabelle plums in the garden. On the tenth day I made greengage jam. I love making jam (not so keen on eating it, but I manage)
Oh, about that, plums and greengages etc have their own pectin, so I use half jam sugar and half normal granulated, and that works fine.
Find blackberry jam alone too seedy - so make either blackberry and apple (sometimes have to freeze blackberries while waiting for the apples to ripen a bit!) or blackberry jelly which is quite the most delicious preserve ever..