Does she have a dark corner to go to that is new? Did you put a sleepy hut in her cage recently? I don't think it's unusual for birds to lay eggs when they reach a certain age. Are you feeding her healthier? There are lots of reasons that could cause the change. First thing to do is figure out if you are doing anything differently.
Going forward, you may want to cut down on the extended daylight exposure if she's been going to bed late, as well as any potential nesting areas and foods too rich in protein. Also, any stroking of her back or beneath her wings might also be giving her that "loving feeling". These are all hormonal triggers.
As for advice pertinent to the moment, I'd advise that you do not remove the egg if she is sitting it. Another one or two may be coming along in the next few days, too. Removing the egg before she abandons it might just encourage her to lay more to replace it. If you can, once she's finished laying, replace her eggs with dummy eggs. And then let her sit them until she realizes they are non-viable and abandons them.
Of course, all this is assuming that she has laid a non-viable egg in the first place. Any males around?