I can't think of a good spear fight in text to draw on. There is a good one in the early scenes of the movie Hero with Jet Li.
The spear - Your vampire has the best weapon of the lot. The big advantage of the spear is its length. The humans will have to cross through her killing range before they can even hit her. Once they get inside her range, she loses her advantage, but it;s always possible to get that advantage back by moving away from them. Her main attack is a thrust, which is limiting, but it's also very hard to parry. Also, the tip of the spear is very quick. The length of the weapon means that a small move on her end translates to a big, fast move with he point. In other words, she's going to be able to get back into her fighting stance much more quickly than either of the humans.
Mice is right, their best bet is to try to get in close and eliminate her advantage. If they're fighting in a room the tight space will help them do this. If they're outside I wouldn't give much for their chances. If she thrusts and misses, one of the humans could try to grab the spear and lock it under his arm. That's dangerous but would leave her weaponless.
(If your vampire is smart, and has been in a few fights, she'll be prepared for this. Knowing that there are situations where her spear won't work, she should have a back-up weapon like a long knife, or a small automatic pistol.
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The baseball bat - This is the second best weapon in the fight. Because of it's shape the bat concentrates it's power near the tip and delivers a powerful impact. That's also a disadvantage. The heavy tip of the bat means it's not a very agile weapon and it's hard to parry incoming attacks (especially thrusts) with it. It's used with a powerful swinging motion and is slower which leaves the wielder open to counterattacks more than the spear does. In other words, the bat is a good offensive weapon but not so hot on defense. That's who similar weapons (axes, maces, etc) were usually paired with a shield historically.
The pair of stakes - These are, by far, the weakest weapons in the fight. They are relatively short weapons, which makes their defensive use very limited. This character is not going to be able to use his weapons as any kind of good defense against the thrusts of the spear. The stakes are a little like big knives, but they don't have sharp weapons and can't make any attack other than a thrust. Worse, they aren't very good thrusting weapons. A sharp wooden point it still pretty dull by weapon standards and is going to need to have tremendous force behind it to get through muscle, ribs or sternum.
They dealt with this in Buffy by basically making any blow to the chest with a stake fatal. In from dusk to Dawn they suggested that there was some strange vulnerability in a vampire's body that allowed wooden weapons to punch through the chest. Barring something like this, the only realistic way to get a stake through a vampire's heart is to go old school. You have to drive the stake in with a hammer...something that is not practical in a combat situation.
