Milord, this is how I imagine someone less liberal than us might see those drawbacks:
A tool to ensure obedience
Compliance
Preserved innocence
Experiences that are best avoided
inability to have a normal social life
Define normal. Many people want to establish sexlessness and modesty as a norm and seek out social circles where it is.
inability to develop a positive view of sex
A small price to pay for establishing a negative view of sexual immorality. A married-off daughter only needs to have sex enough times to make grandbabies, and it is fine if she experiences that act as a sacrifice.
Not inherently bad if it does not lead to immoral acts
potential nevrotic issues
Can happen with a sex life as well
Builds character
A penance for immoral thoughts
Hopefully for a good cause
Hopefully for the better
possible future legal issues
Proper discipline will take care of that for most people
That is why you need to persuade her that doing that is the right thing.
Some things are downplayed easily. Others might even look slightly positive.