Mareechiravadhat, sarvalokanayakaa brahmasakthihee, vynayakee maya siddhalakshmi vallabhaa, thatpathi paramatmaa vallabheshahaa !
This sloka is from Vallabheshopanishad
It tells us that consort of parabramha (here taken as Gajannana) is mula prakriti and she acts as the maya of parabrahma (Vinayaka) and is Siddhalakshmi and that is why he is called as Vallabhesha.
I will also take the opportunity to differentiate the MahaGanapati and LakshmiGanapti mantras as said by the above Upanishad.
Following the first six bijaksharas, (Tara, Sree, Sakthi, Kandarpa, Krodha, Vigensha) (Om, Sreem, Hreem, Kleem, Gluam, Gam), the mahaganapati sadhana is 'ganapthe varada varada' whereas lakshmiganapti sadhana is 'ganapthaye varavarada' . The difference is seen in the goal of the sadhana, Mahaganapati is used for Moksha whereas LakshmiGanapati has become famous as giver of aishwarya.
I believe it is this essence of the mantra (the aishwarya prasada) that famously gives it the name Lakshmi Ganapti (since Lakshmi is aishwarya ).