To buy 2 theatre tickets as a gift but expect to be given 1 ticket so I can attend?

[Cuppaand2biscuits]

I've just noticed a theatre production of a movie that my sister and I loved is coming to our local theatre. I would love to get her tickets for her birthday, I would also love to see it myself. The tickets are nearly £40, I really can only afford 2 tickets.
Can I tell her that I want to go or let her choose between me and her partner (who may or may not be interested in seeing it )

This reminds me of the time i got a mate 2 tickets to a concert as a present and he invited me with the second ticket. I bought 2 more tickets for the same concert as a favour for a mutual friend as he didnt get paid for a few weeks and was worried they'd sell out, deal being he'd pay me back. We became decent friends (or so i thought) in the next month so i let him have them as a birthday present too. So i keep 1 ticket, send other 3 in post to second guy (best friends with the first guy, saw each other every weekend where as due to MH i'd actually met neither in person yet but did few weeks prior to concert.)
First guy then gets a new gf he wanted to come along, second guy (who hadn't passed on the ticket yet) offers to sell his spare to him so gf can come with.
I felt SO awkward, despite the fact he could have given his mate the ticket for nothing as they were a present from me he'd got for free and he didn't have anyone in mind to ask along anyway, he wouldn't. Nor would he have me as his "guest" with his spare and pass 2 tickets on to first guy (general admission so would all be together anyway) so he could use his second one for his gf, because they "belonged" to him and he always intended whoever he took with his second ticket to buy it off him despite them being a gift!. I ended up buying the "spare" ticket back off guy 2 to give to guy 1's gf who i'd never even spoken to, so he didn't get put in an awkward position of asking me to not come or buying back half his birthday present.
So not only did i buy all 4 tickets, pay 2 lots of handling fees and postage, and pay to post 3 of them to him, but i then had to pay face value of one of the tickets to buy it off him so guy 1's gf could go along because of his greedy unreasonableness!
Bastard went on to ask to "borrow" £40 the month after as he hadn't budgeted his wages to get his dad a fathers day present. I went out of my way to go out, meet him and give him the money, for him to shoot off straight home after. I tried to chat as normal later that night, and he ignored me. He ignored every text, msn message email or facebook message i sent him ever again, even when i politely asked 3 months later as it was a weeks worth of rent and i was desperate, didn't even reply to say he didn't have it, i honestly would have preferred he laughed in my face and say he was never paying it back than just ignore me.
Bumped in to him 3 days after my mum died, asked how he was etc. I mentioned my mum had just died and he went "yeah i know" and looked at me as if to say "so what? i don't care"

It's fine OP. Just make a pretty voucher to put in a card saying "We are going to see for your birthday!" and that's her present.

My sis did the same for me with Harry Potter.

Ha! My sister bought me a ticket for a show for Christmas and I bought her one too! So we effectively both bought a ticket each and had a lovely long day out together, drinking cocktails & hanging out but pretty much at cost-neutral I paid for her & she paid for me for the same things. We do this often to 'treat' each other to things we both enjoy. The real gift is doing them together, as we live around 200 miles away from each other & travel is expensive.