It all sounds ghastly GG, in my humble opinion. What you shared above with her literally showing he underwear is extremely wrong and unprofessional. To have it pointed out, and she's it'll wears inappropriate clothing is wrong on so many levels. Have you raised the issue with her again? What on earth does she say if you tell her 'I can clearly see you're wearing x colour underwear - it's making me uncomfortable and it's very unprofessional' ???

Reading what you wrote and then what TN wrote, my thought on it all is maybe you are drawn to her and are seeking (unconsciously) to repeat the previous trauma pattern / traumatic bond - but the main reason being so you can gain a sense of mastery or control over the relationship dynamic? Ie - you're older, wiser, smarter now, than you were as a child, so in theory have more 'control' or 'power' over the situation now than when you were little? Ie - at a deeper level, you're trying to 'change the ending'?

(Hope that doesn't come across as a criticism cos it's not - I don't mean it in a bad way or mean to imply you're doing it on purpose or are being manipulative etc - really hope it doesn't read like that!)