1. She may be napping too long during the day.
2. You may be trying to put her down to bed too early.
3. She may need a better bedtime routine (warm bath, massage, nurse or bottle, story, snuggle etc).
4. She may be hungry.
5. She may be teething.
It is hard when they can't tell you. There are many reasons this can happen. It is very normal at 7 months. Decide what is best for you. It is ok to let her cry it out (a little bit). It is also ok to not do that and to just snuggle and feed her.
See if you can first isolate the cause, and then go about remedying it. I would personally make sure she doesn't nap too much during the day and she is on a good schedule of eating and sleeping and make sure she has a good bedtime routine. There are sample schedules for your baby's age that you can look at online. One ex:
wake up 7 am change, feed then play
nap 1 10 am - 11:30 or 12 pm
change, feed, play
nap 2 2 pm - 3:30 or 4 pm
change, feed, play
bedtime routine starts at 6:30, bath, massage, story, snuggle, feed etc and to bed by 7:30 pm.
Just an example. She should be getting 13 - 15 hours of total sleep per day between naps and bedtime at her age.
Good luck and enjoy!!!! My youngest baby is 2 1/2 now. sniffle...