I teach my staff that their client is paying for a professional service. They obviously want to know about treatments that we offer, otherwise they wouldn't be coming in. It's not logical to pay for a mani and not be interested in a gel application, or to have 9 gorgeous nails and not get an enhancement on a broken nail. You have to think about value, sometimes it's better value to spend a bit more.
You should focus on aftercare. At the end of the mani you should tell your client when she needs to have her gels removed and get that booked in so she's not looking scruffy. Ask if the same day and time will suit her and check you're availability. When you're getting that booked, ask if she wants a re-application at the same time.
Concentrate on getting your clients rebooked First. Once you've had them return a couple of times you can start upselling. Your client is most influenced by one of these three factors 1) what's new 2) what other people are trying 3) not being left out? You need to chat to your client to establish in your mind whether she is a trend setter and wants to try new things - a newly released or daring colour or shape, or whether she is influenced by others "my clients are asking for X" or "pretty much all of my clients are having an IBX as part of their treatment now, it makes such a difference".
You also need to think about linked sales. In Starbucks the staff are trained which food goes best with which drink based on sales so they know for instance that the most popular purchase with say a latte is a raspberry muffin. So every latte customer not asking for food will be asked would you like a raspberry muffin. Clever no?
Finally you have to flip your reluctance to discuss or suggest treatments with your clients on its head. How does your client feel if you don't do this? Does she feel judged? Does she think that you don't want her in your salon?. I have a client who told me that she wasn't happy with her hairdresser and wanted a change. Her complaint? "I think I'm a bit too old and unfashionable for them. I don't think they are very interested in me". Because they didn't try and suggest new things to her, she felt unwanted and was looking elsewhere. So don't risk losing clients because yoiu don't seem to want them to return.