Linkedin is for business connections with other business or people with who/whom you might later build a meaningful or profitable business relationship, NOT a social media type relationship.
So you need to get straight to the point politely and say immediately what your business does, what you hope to receive back and how the two of you [business or personal] could build a mutually beneficial relationship.
Me: Hello (her name)! I found your name in (the name of a course) group.
I Run/do/own/organise whatever. (it must be something you think would benefit them/her/he)
I would like to introduce you to [whatever the services you can offer)
I am available (state the times or when you are at the office etc)
Please feel free to contact me at anytime, to answer any questions.
Looking forward to working with you/ hearing from you / your reply
Regards [YOUR NAME]
[YOUR POSITION IN THE] organisation or whatever it is.
She: Hey it's nice to hear from you.
Me: Hello Good morning (her name) [use hi later if she initiates using hi or that type of business relationship later develops]
Me: Thank you for getting back to me.
( in here you have to start chit chat or begin informal business chat at this early stage)
She: How are you?
Me: Very good, thank you! How are you? Do you like (the course we both do now)?
She: Yes, I do
How can I help you?
Me: (state exactly what you want)
Be careful not to mistype fell like I did initially, that is to do with sewing. not feelings or emotions.