Isabelle is very aware, because part of why she pursues the people she does is because their toxic tendencies are very apparent and so she doesn't feel like she'll get a nasty surprise later. It's easier if she knows all along.

She does actively choose it for that reason, since it soothes her fears, but also if she stopped she would definitely feel the lack. Isabelle spent her entire childhood under the extremely comprehensive oppression of an abusive man, and it's what feels right to her on both conscious and unconscious levels. It's a hard habit to kick.

As for how she feels about it, that depends on how her mental health and love life have been. Sometimes she tries to do better, but most of the time she accepts it because she thinks it's better than trying to date someone she thinks is nice only to end up abused anyway without having seen it coming.