More weight = more braking required
More weight above the COG (centre of gravity) = less stable
The steering will be completely different.
So, as per my first reply, be smooth
And ride slower until you get used to a pillion on the bike and the different feel.
Although you should always be looking ahead, react sooner like gently closing the throttle before you normally would.
Arrange signals that you both understand
eg:
If the pillion want to stop, a few taps on you shoulder, or grips round you waist.
Junctions...Pillion tapping you on the shoulder then pointing in the direction on turn, ie left shoulder for left turn...might sound obvious, but some it can take a while for a non driving/riding passenger to think about road sense.
Sort out what the pillion will hold on to.
My three kids do different things.
One holds onto the grab bars at the side.
One holds on to the jacket at the waist, so I bough one of those belt with handles for pillions to hold on to.
One doesn’t hold onto anything, “because I don’t need to†he says.
If going over rough stuff or, a series of quick bends, or filtering where you might need to stop or change direction quickly, I always indicate for the pillion to hold on, even my lad that is so cofedent on the bike.
Last tip for now...if doing long distances, keep communicating with the pillion, as they might go to sleep... no kidding.
Consider getting “wired for sound†(or wireless) so you can talk on the move.
And, the tip after the last tip...you relax and enjoy.
The first couple of times I took my kids on the bike, I was so tense that I was riding like sh!te (no change there some will say).
So, chill and enjoy.
If you are OK, then you lass will be OK.