Is never being single in your adult life a red flag?

I (25M) was dating someone I met on tinder (26F) that didn't work out, but I'm now in the phase where I'm trying to learn some lessons from the past. She came on strong, always super excited to see me and talk/texted all the time for a few months. Towards the end she told me she has had 6 boyfriend's and has never been single for very long since she started dating. Red flag? She also kept talking about her most recent ex, and while not being absolutely irate or anything she was a bit passive aggressive about everything. The later ones I'm not realizing were red flags, but I'm mainly focused on not ever being single in your adult life. Thoughts?