Oh I have to disagree with you there. I don't think Barn ever led Julia on. If there was ever a conversation about their setting off on a life together while he was secretly seeing Maggie, then he would have been leading her on. However, IIRC, nothing like that ever happened. The movie version did nothing nice for either Julia or Barnabas in terms of character. The movie did make Julia look pretty bad right next to Barnabas.
The movie set up Julia's betrayal of Barnabas quite early. Julia was shown being unhappy or disappointed that while Barnabas was thanking her up and down for all of her help, he was planning on giving Josette's music box to Maggie whom he stated meant a great deal to him. Obviously at that point, who stood where was made pretty clear from Barnabas' standpoint. It certainly sucks for Julia that he would feel that way, but he did not ever hide the fact he was interested in Maggie and wanted to "woo" her at every opportunity. The gift of the music box was a romantic gesture.
Julia watched Barn and Maggie stroll the grounds in the daylight, an achievement made possible by Julia. The look on her face watching them was not one of bliss. She was not a happy camper and later in some conversation Julia let it be obvious how she felt and Barnabas said he had "no idea" that's how she felt about him or words to that effect. (If I am misremembering, please tell me). Julia was angry and hurt and since Barnabas was only able to court Maggie like a normal man only for Julia, she sought to take it away from him. Was her anger understandable? I think it was. But Barnabas did not treat her as a potential love interest otherwise he would have given her the music box while going on and on about all that Julia had made possible for him in this new life. So, Julia's response was to turn him into back into what would be his natural age (kiss that, Maggie!) which was also a death sentence. She tried to beat it out of town but got busted by Barn. The implication being she would cure him but only if he would be hers in the process. Otherwise, all bets off.
Like I said, the depiction of Julia in the movie was far from flattering and different from the series. The series Julia would not have done that to Barnabas, IMO.
Nancy
Point being? Yes she betrayed him but it's not like she was the villan or something. He led her on. .He was evil and got staked.