Regardless of what she is doing, demons all spirits once summoned are hard to get rid of. Plus you run into the ones that claim to be one thing and are actually another. demons that claim to be angels, mischievous fey that claim to be ghosts etc. caution should be approached at every turn when dealing with the almost seen.
The demons that you speak of would be considered of the Succubus demonic family. Succubi (or Incubi/ male succubi) love to "haunt" those who drive for sexual attention. They lay with those on an astral level and corrupt their victims into believing that the "sex" is harmless. As they lay with their victims, they take away their energy and like I said before corrupt their victims. Succubi are very dangerous creatures. I would NOT suggest your friend to summon one.
As a person who knows some demons, they vary as much as people do. The terms demons and angels were used interchangably untill a few hundred years ago. The church used them as a type of 'propoganda' to say. Like the boogy monster. You don't go in the closet, so the boogy monster can't get you. You don't turn away from God, so then the big bad demon can't get you. Angels can be highly annoying.
Angels aren't stuck up if approached with respect. They deserve respect after all on the spiritual hierarchy they are higher than us.
But like someone said above ALL beings vary just like people; some people I don't get along with whereas others will get along with them. The same applies for deities.
yes, they can. it's been mentioned before, but succubus/incubus are demons who 'feed' off of energy during sex. demon's are evil, but they are dangerous, especially if you don't know what you're doing. when dealing with a demon you need to research like mad. learn everything you can about them, their strengths, weaknesses, how to conjure and of course dispell them. you need to protect yourself and be prepared for anything. they are powerful, and typically will do only what's best for them.