In season 7 she trusted him more than he trusted himself.

Anyone who thinks she didn't trust him by the end of the series is kidding themselves.

She definitely trusted him in season 7, but there were traces of it much earlier, after all you don't ask someone you don't trust to look after your sister.

Obviously otherwise she wouldn't have taken his chip out.

umm yeah. Earlier in the series no, thats why he was tied up. But the question was if she "EVER trusted Spike" and at the end, YEAH she did. like A LOT. i agree with goodbyemra, she wouldn't have taken his chip out if she didn't.

Of course...

she trusted him enough to have her mother and sister stay with him and help to fight with glory and he also fought with the scooby gang so she had to have some level of trust and she would always go to him when she had problems.

Yeah Buffy said her self in season 7 - after Giles sent Spike away - Buffy said how " how can u send way the only person that's had my back "

By the end of season 7 she trusted him with eyes closed. The way she could never trust anyone else. And he trusted her just as much. And the level of trust they reached in season 7 was the result of their whole journey, of them going through so much together. I don't think Buffy trusted Spike in season 2 at all, but they could work so well as a team and they had a special level of understanding, that's why she could leave her mom in one room with him (and back then he didn't even have a chip) knowing he wouldn't hurt Joyce. It wasn't trust yet, but there was understanding. Later, in season 5, she trusted him with her family, she counted on him to protect Dawn. That was a foundation for trust. And by the end of the show Buffy trusted Spike more than she truated her closest friends imo.