My friend is convinced her new house is haunted. I went around to help her decorate and make her feel better. But I don’t think I helped.

A friend of mine had the same problem years ago. Doors would slam on calm non windy days and things would be hidden, etc. I suggested if she has anything to do with the occult like fortune telling, anything about horoscopes, antiques, witchcraft, to get rid of it. She said she would and then the door slamming, etc stopped.
My daughter collected Egyptian statues and then she saw Egyptian mask like entities come near her face at night, a broom appeared floating in her bedroom door, etc. I told her to box the statues up and either sell or destroy them. She only boxed them up and they are still in storage but the weird paranormal sightings stopped.
Never allow weird shit into your house!!!

Your friend can contact a psychic or medium to see if the spirits are friendly or not. Also, the city you live in or the area surrounding your friend's house probably has a long history of people meeting an untimely death, which can explain the paranormal activity.

my friend bought a house that an older couple had lived in but had died. she said her house was haunted by the couple. she put in electronic toilets and the ghosts messed with them and kept flushing them all night long. she had to have them removed. she had other things happen too but they seem to be ok now.

Not 88 Grantley Gardens by any chance. I lived there. If it is I know the spirit, I got her to leave once before...

You can try talking to the spirits. If does not help, may need to call some one in that can help.

Many options. Some are none standard.

I'm one of the few that ghost's avoid.

Sounds like the house really is haunted. Do you believe it's haunted? Have you experienced ghosts before? 👻

You could do a cleansing ritual or a seance to identify the spirit, determine its grievance, and then either make peace with it our convince it to leave (move on).

👀 I'd be staying over just to investigate tbh because

Sage the house

There's a few things to do.

1. Ignore it
2. Talk to it
3. Sage it

see if the local priest will bless the place

Tell her to tell it to leave. Tell it that it doesn't belong here among the living.

She should call ghostbusters!