A male angelfish is necessary to fertilize the eggs After they are laid (unlike livebearers), so these eggs will be infertile. My angel fish did the same thing. We removed the eggs because she was being such a bully to her tank mates to protect them, but in our tank she is the biggest thing.
Like Mcasella says, its actually pretty normal for some females to lay eggs on their own (hen chickens do it all the time). You'll just have infertile eggs, so its just some free food for everyone else.
She really does need to release the eggs so this is a good thing. As others have said they won't be viable eggs because there is no male to fertilize them but if she didn't release them they would just keep building up inside her. Some may be reabsorbed but maybe not all of them.
Eventually she could become egg bound and most likely die. That actually happened to one of my female zebra danios I have no idea as to why she held on to them since I also have males in there.