How do I portray a character that's drunk? I'm 15 so I have no experience with alcohol and one of my characters is going out for a drink with another, and one of my headcanons is that she gets drunk easily. Help please?

Symptoms that can come with being drunk:

• Lowered inhibitions
  Your character may say or do things that they wouldn’t even think of doing were they sober. However, proper decision-making and thoughtfulness are inhibited when under the effects of alcohol. This can include improper touching, gossiping, telling personal secrets, etc.
•  Impaired Vision and Depth Perception
  Alcohol consumption can cause vision impairment and make it difficult for someone to navigate themselves properly. It can also cause a lack of depth perception, which can be troublesome if someone is reaching for something and finds themselves continuously reaching for it, as it is farther away than they are seeing it.
• Vertigo
  The atmosphere of the character may become distorted, giving a sense of vertigo or a spinning room. 
•  Frequent urination
  As alcohol is going through your system, it can cause frequent urination depending on the amount consumed. With this, a person can easily become dehydrated as this is a side-effect.
•  Stumbling
  This relates to the impaired vision and vertigo as well. A person may not feel completely in control of their body and often stumble around from disoriented balance, causing them to stumble, crash into objects/people.
• Slurred Speech
  Know that this isn’t something that happens all the time. The entirety of their speech may or may not be slurred. Here is an example: “I’m not friggin’ drunk. Whateryouuu talkin’ about.” It is often times partial, as well as shoving words together to make ‘new’ words. 
• Light headed/Tingling sensations
  Exactly as this section suggests, the person may feel light headed and/or tingling sensations in their arms or legs.

Now for the types of drunks:

• The Angry Drunk
  This kind of drunk gets mad at just about everything and everyone. If someone has ever done something wrong to them, well, they’re going to want to start a fight. Someone doesn’t want to make out with them/get touchy? They become furious and accuse them of this and that, call them horrible names, and so on. Often times they can become extremely violent even when someone is just trying to help them stand up straight.
• The Sleepy Drunk
  These drunks aren’t too exciting at parties, because all they want to do is sleep! Alcohol hits them pretty hard and they feel sleepy/go to sleep where ever it is they happen to be.
• The Happy Drunk
  These drunks become more social, loud, and giggly. They can be very touchy and close with the people around them, and can be quite the talkers. These types of drunks are the ones that want to dance and have a good time.
• The Depressed Drunk
  Crying loudly, bringing up painful memories, talking about exes, pets that passed away are just some of the things that you can expect for this type of drunk. They just want someone to listen to their woes and problems, all the while sobbing as they continue to drink.
• The Melancholy Drunk
  Not to be confused with the Depressed drunk, this type of drunk is often a loner and just stews in their own sad thoughts. They may cry, but to themselves, and are all around mopey.
• The Casual Drunk
  This type of drunk doesn’t steer too far from their usual self. They may be a little more social and louder than usual, but other than that, they’re pretty much the same concerning their personality.

Note that a lot of these involve a decent amount of alcohol consumption, so know that you will want to tone a lot of this down if your character isn’t drinking much at all. The types of drunks mentioned are just stereotypes and you can mix and match to create what fits your character the best. I hope this helps!