there is no mist coming out... is it broken? i can feel a very weak blow of air coming out from the nozzle.. but no mist. any idea what's wrong?

I know how to fix this, because I have an old one that I bought 5 or 6 years ago that worked great, so I could compare the new one that I bought in March of 2022 to the old one. I found that the problem with the newer ones is entirely with the tank, and you can fix it with 2 simple modifications. The base unit is ok. So here is what I found about the tank. The newer one that put out hardly any mist at all has a thin ring attached to the bottom of the tank with 6 thin plastic legs. The ring has a hole in the center that is 1/2" in diameter. The OD of the ring is 1.125 inches. This ring blocks most of the water and mist from going up into the tunnel to the top. The old one doesn't have this ring at all. It was easy to cut off since the 6 legs are thin plastic. So I cut the 6 legs and took that ring out of there. Then I noticed that the nozzle on the very top of the tank has a fin in it. The old tank doesn't have that fin at all. I also noticed that the hole in the top of the nozzle was just slightly smaller than the hole in the old unit's nozzle. The new unit had a nozzle hole a little under 1/2" while the old unit has a hole that is almost exactly 1/2". So I put a 1/2" drill bit into a drill and drilled out that hole. This at once got that fin cut out of there and enlarged the hole to 1/2" diameter. Presto. Now the new unit works just like the old unit. Puts out an entire tank in about 12 hours. Perfect, just like the old one was. BTW the old one ran for about 4 or 5 years (winter use only) before it quit working. Pretty good. Obviously they made a bad design change at some point and they should change it back to how the old ones were.

Is it easy to fill it with the water? I am buying it for my 85 year old mom.

You have to take out the top part and turn it up side down, open the cap, then fill with water. For your 85 years old mom, it really dependents on her situation.

Is there any safe way to add aromatherapy/essential oils?

I've been adding about five to ten drops into the tank every refill. I've been doing this for three months. Just make sure you clean the tank and base at least once a week. Use vinegar and warm water to clean both. By the way, I've only needed to use five drops of young living essential oils since these oils are highly potent.

Can you put essential oils in this humidifer?

I use only distilled water. Oils will make cleaning and deordorising close to impossible. I would add a tablespoon or two of Rose water, orange blossom water - nothing oil based.