You could try to push yourself "more" instead:

Try riding a bigger gear, pedalling with one foot (if you have clipless pedals, this will help you achieving a round pedalling technique), standing up, etc. Practice riding with the brakes (useful skill for paceline riding).

Maybe you can convince your friend to do a few sprints with you? Sprint (all out up to the next lamp post/red house/etc.) and then ride a very relaxed pace. I did that with a friend of mine, a very leisurely cyclist who had no other intentions than having a good time on the road. It made her laugh really hard and she enjoyed that. (Last one at the lamp post/red house/etc. pays for ice cream. You can do a best of 5 for these and that gives you an intervals session!)

If there are hills, do them twice.

I think you could explain your goals to your riding partner in a reasonable manner, maybe she'll understand, especially if you have some specific objective (ex: ride xyz century in a given time).

Try to find other riding partners who are stronger than you, or ride alone sometimes, maybe....

Good luck!