You said "still not on a routine" which implies that this has been a continuous problem and didn't just start recently because of teething or anything. Is she on a routine during the day - eating around the same times, followed by playtime or activity, then a nap? Do you wake her up if she takes longer than a 3 hour nap during the day so she'll sleep longer at night? Do you have a bedtime routine that you follow every night with her to help her wind down? Perhaps you could try putting her to bed a little later and see if she sleeps through (just for a little while and then you can move it back 15 minutes a day until you get back to her normal bedtime). If you think the problem is teething, you could proactively give her Motrin at bedtime; it lasts longer than Tylenol and our pediatrician recommends it at night for teething. If she's waking up wanting to play, though, and not tired and in pain, it's probably not a teething problem, it's more of a habit that she wants you to be with her. So, you have to teach her that that's not how it works anymore, in whatever way you can and are comfortable with to change the way things have been going. I agree with the other poster, don't pick her up at night or give in to her wanting to play; it's not playtime, it's bedtime and you have to teach her that. You can still go in and reassure her that you didn't abandon her, but lay her back down and reiterate that it's not time to play, it's time to sleep. It helps to keep your mindset in the perspective that you're doing what's best for HER, she needs her sleep in order to grow and be healthy, even if she doesn't WANT to sleep.
If you want to try letting her cry it out, I highly recommend the book "Solve Your Child's Sleep Problem" by Dr. Richard Ferber. It is more of a managed cry it out system that is very specific to keep you from going insane from the crying, but it really only takes a couple days to a week to be effective, as long as you're consistent. You don't just let them scream until they're so exhausted they fall asleep or your go insane, you go in at specific intervals to reassure them that you didn't abandon them but reiterate that you're not going to give in as you've done in the past. There is going to be some crying because she's going to be mad that you're not following the "rules," but she'll quickly catch on to the new rules as long as you're consistent and don't cave in. This system even worked with my stubborn DD who would sit up and scream bloody murder as soon as I'd turn around to take one step towards leaving the room! (This is the DD that I would rock to sleep for 20-40 minutes only to try to set her down and have her be wide awake and start screaming, so I'd have to rock her all over again; it would take all day to put her down for a nap! When I changed the rules, she was NOT happy, but I swear it only took her a couple days and I got my life back and a baby that I could just put down at naptime and bedtime, sometimes she would cry for a minute or 2 and then fall alseep.) I didn't think anything would work with her! (BTW, I tried "The No-Cry Sleep Solution" first, but it didn't work because I'd go in to calm her down like you're supposed to, but as soon as I'd turn around after she was calm, she'd start screaming because she didn't want me to leave, so that system was ineffective for my stubborn DD. There was no "no cry" in her sleep solution.
Another helpful book for getting them on a routine is "On Becoming Babywise." It focuses on setting up your daytime routine so that nighttime sleep will naturally follow. I started out doing this with DS (he's 3 months today), and he started sleeping through the night on his own long before DD did, and we had to force the issue with her but not with him.
If your routine during the day is working well, you just have a stubborn one at night, "Healthy Sleep Habits, Happy Baby" is a good resource as well. It has tips and tricks for upsetting their habits and getting them back on track. DD (she's 2 1/2 now) stopped taking her afternoon nap around the age of 2 but still needed it, and the book had us putting her to bed at 5:30pm for 4-5 days to reset her naptime. I thought it was completely ludicrous but I was desparate to try anything. It turned out that she really was just overtired and couldn't take a nap, even though she'd been getting adequate sleep at night. After the first night of putting her to bed at 5:30 pm (she fought us tooth and nail but eventually fell asleep), she still woke up at her normal time (I braced myself for a 5:30am wake time but was pleasantly surprised), and she took a 2-hour nap the next day, something she hadn't done in months.
DD is still my difficult sleeper, but these resources helped me to at least get her to sleep through the night and get enough rest to function and not be so crabby. We still have to put her to bed early a couple days a week (not 5:30pm early, that's before DH even gets home from work) because she still doesn't take a nap every day, but some days she does, which is better than the few months she wasn't taking a nap at all but still going to bed at 8pm. I put her in her crib for downtime every afternoon whether or not she sleeps (she's good and will play, sing and talk by herself, so she's not screaming or anything) and that helps some.