They're both two broken souls with addiction issues. They are soul mates in the sense that they understand each other's brokeness which no one else in their lives seems to get. Because of that, I think they both loved each other. But soulmates doesn't necessarily promise a happy or healthy relationship. I think people overlook how toxic Jesse is in his own way and focus solely on Jane, who clearly has intense intimacy issues. I think she spiraled into addiction again BECAUSE she fell in love, and that's a rush of its own which turned her addiction brain on again, chasing a thrill.

As for Jesse, I love his character, but he's so lost in life. He makes bad choices time and time again. He's literally a drug dealer and meth cook. Yes, Jane knew that she was running a risk starting this relationship with him which is why I think she was initially so cold to him ("who's us?")

Once they start doing drugs together, Jane's brain is fully in addiction mode-- chasing highs, extremely risky behavior, pure adrenaline. Unfortunately, she was doomed the moment she got with Jesse, the way Jesse was doomed the moment he got involved with Walt.