Just a few thoughts on the whole issue:
1. House elves, especially when given a fey background, would most likely not be able to attack people. Defend them, at most. Otherwise we would have heard about assassinations or at least massive prank wars before. Let's just say vampire rules apply: House elves can't act without proper permission. If they aren't invited in, they can't interfere with a home. Probably the reason why they aren't used to deliver mail, too.
2. Taylor could use owls to deliver bombs, she doesn't need to rely on house elves. This would make timing things complicated though and limit the payload.
3. While it would be possible to deliver dangerous packages to Death Eaters, their homes might be protected. There might be magic to warn of danger or their house elves would intervene. Doesn't Gringotts employ some of that?
4. Wards are not a thing in the Potterverse. Those are charms and jinxes. Or possibly even ritual/blood magic in case of the Dursley home.
5. To get past defensive magic you'd need to use mundane explosives or toxins, anything magical would probably be detected instantly. And I wouldn't want to bet C4 would get past any spell that is checking for danger or malicious intent.
6. Where would Taylor get mundane explosives in 90s Britain? She'd have to raid the army. Which would be discovered quickly since this is during The Troubles and people are paying a lot of attention to explosives, weapons and ammo. She'd have to get a skilled wizard on her side for apparition, memory charms and possibly an invisibility cloak just to stand a chance.
7. The Order of the Phoenix would most likely be opposed to the entire thing and rightfully bring up the point that this is going to get innocents killed. Bombs are indiscriminate.
8. Even if Taylor somehow managed to overcome all those hurdles and blew up Malfoy mansion, there's no guarantee she'd actually manage to kill Lucius. He might be able to apparate away or have a protective charm on his person or use house elves to open packages for him. I'd be surprised if there wasn't some sort of security routine done for packages from unknown senders. At least one wizard in the past must have sent a cursed object to an enemy, so people aren't just going to touch everything they receive. The magicals aren't completely incompetent and stupid after all.
9. Assassins/bombs rely on surprise to work. Once Voldy or the Death Eaters are warned the whole thing is not going to work anymore. Even worse, I can totally see Voldy coming up with his own version and sending dark magic bombs to his enemies.
10. Escalation isn't your friend when you lack the knowledge, skill and resources to go as far as your enemies. At this point Taylor needs to worry to stay healthy and sane, she needs to concentrate on defense. After all, she's going to Hogwarts and she has basically no magic. Any first year can send her to Madame Pomfrey with a minor prank. Her only option right now is lethal surprise attacks, which is not something she can use in a school.
11. I'm fairly certain wizards have spells against bugs. Just to keep their homes free from pests. Once people are aware of Taylor, those spells will be used everywhere.