New sleep issue

So my sweet little lady would usually go down around 7pm and sleep until at least past midnight until she needed her first feeding. Most of the time she would sleep until 2-3am. She would nurse then go back down until 7-8am. WELL for the past wk she has started only sleeping for 30-45 min before she gets up. She'll go down around 7pm and is always up before 8pm. She doesn't seem happy to be up. Two nights I was able to nurse her after she woke up and she went back down right away. It is REALLY getting frustrating. Our bedtime routine is the exact same every night. I'm at a loss of what to do to fix it :( I have 2 other little ones to put to bed after her so its hard to be up dealing with her before I get them down around 815pm. Overall, her sleep has been a little off. She is getting up more frequently throughout the night. For about 2 months she would go down around 7pm, wake between 2-3am, nurse and sleep until 7-8am. I wasn't expecting that pattern to stick for ever but this whole getting up before 8pm is really exhausting. Any insight or maybe other mommas are experiencing similar issues???